Add credentialless as a recognized boolean attribute for iframes (#36148)

## Summary

The `credentialless` attribute is a boolean HTML attribute for
`<iframe>` elements that loads the iframe in a new, ephemeral context
without access to the parent's credentials (cookies, client
certificates, etc.). This change adds it to all boolean attribute
switch/case lists in React DOM so it is properly handled as a boolean
(set when true, removed when false) rather than being treated as an
unknown string attribute.

Per the [Anonymous iframe spec
(WICG)](https://wicg.github.io/anonymous-iframe/):

> The credentialless attribute enables loading documents hosted by the
iframe with a new and ephemeral storage partition. It is a boolean
value. The default is false.

```
partial interface HTMLIFrameElement {
  attribute boolean credentialless;
};
```

Changes:
- ReactDOMComponent.js: Added to both `setProp` and
`diffHydratedGenericElement`
- ReactFizzConfigDOM.js: Added to `pushAttribute` for server-side
rendering
- ReactDOMUnknownPropertyHook.js: Added to both validation switch/case
lists

## Test plan

- Added unit test in DOMPropertyOperations-test.js verifying
`credentialless={true}` sets the attribute to `''` and
`credentialless={false}` removes it
- All tests pass in source and www channels (590 tests each)
- Flow type checking passes (dom-node renderer)
- Prettier and lint pass

DiffTrain build for [306a01b](306a01b)

Author: hoxyq

compiled/facebook-www/REVISION

@@ -1 +1 @@
-bc249804d3c2ea6ee95bc5543c3735a65d1239b5
+306a01b4e0242e9379ba971c8925670651f16818

compiled/facebook-www/REVISION_TRANSFORMS

@@ -1 +1 @@
-bc249804d3c2ea6ee95bc5543c3735a65d1239b5
+306a01b4e0242e9379ba971c8925670651f16818

compiled/facebook-www/React-dev.classic.js

@@ -1482,7 +1482,7 @@ __DEV__ &&
     exports.useTransition = function () {
       return resolveDispatcher().useTransition();
     };
-    exports.version = "19.3.0-www-classic-bc249804-20260417";
+    exports.version = "19.3.0-www-classic-306a01b4-20260420";
     "undefined" !== typeof __REACT_DEVTOOLS_GLOBAL_HOOK__ &&
       "function" ===
         typeof __REACT_DEVTOOLS_GLOBAL_HOOK__.registerInternalModuleStop &&

compiled/facebook-www/React-dev.modern.js

@@ -1482,7 +1482,7 @@ __DEV__ &&
     exports.useTransition = function () {
       return resolveDispatcher().useTransition();
     };
-    exports.version = "19.3.0-www-modern-bc249804-20260417";
+    exports.version = "19.3.0-www-modern-306a01b4-20260420";
     "undefined" !== typeof __REACT_DEVTOOLS_GLOBAL_HOOK__ &&
       "function" ===
         typeof __REACT_DEVTOOLS_GLOBAL_HOOK__.registerInternalModuleStop &&

compiled/facebook-www/React-prod.classic.js

@@ -610,4 +610,4 @@ exports.useSyncExternalStore = function (
 exports.useTransition = function () {
   return ReactSharedInternals.H.useTransition();
 };
-exports.version = "19.3.0-www-classic-bc249804-20260417";
+exports.version = "19.3.0-www-classic-306a01b4-20260420";

compiled/facebook-www/React-prod.modern.js

@@ -610,4 +610,4 @@ exports.useSyncExternalStore = function (
 exports.useTransition = function () {
   return ReactSharedInternals.H.useTransition();
 };
-exports.version = "19.3.0-www-modern-bc249804-20260417";
+exports.version = "19.3.0-www-modern-306a01b4-20260420";

compiled/facebook-www/React-profiling.classic.js

@@ -614,7 +614,7 @@ exports.useSyncExternalStore = function (
 exports.useTransition = function () {
   return ReactSharedInternals.H.useTransition();
 };
-exports.version = "19.3.0-www-classic-bc249804-20260417";
+exports.version = "19.3.0-www-classic-306a01b4-20260420";
 "undefined" !== typeof __REACT_DEVTOOLS_GLOBAL_HOOK__ &&
   "function" ===
     typeof __REACT_DEVTOOLS_GLOBAL_HOOK__.registerInternalModuleStop &&

compiled/facebook-www/React-profiling.modern.js

@@ -614,7 +614,7 @@ exports.useSyncExternalStore = function (
 exports.useTransition = function () {
   return ReactSharedInternals.H.useTransition();
 };
-exports.version = "19.3.0-www-modern-bc249804-20260417";
+exports.version = "19.3.0-www-modern-306a01b4-20260420";
 "undefined" !== typeof __REACT_DEVTOOLS_GLOBAL_HOOK__ &&
   "function" ===
     typeof __REACT_DEVTOOLS_GLOBAL_HOOK__.registerInternalModuleStop &&

compiled/facebook-www/ReactART-dev.classic.js

@@ -20434,10 +20434,10 @@ __DEV__ &&
     (function () {
       var internals = {
         bundleType: 1,
-        version: "19.3.0-www-classic-bc249804-20260417",
+        version: "19.3.0-www-classic-306a01b4-20260420",
         rendererPackageName: "react-art",
         currentDispatcherRef: ReactSharedInternals,
-        reconcilerVersion: "19.3.0-www-classic-bc249804-20260417"
+        reconcilerVersion: "19.3.0-www-classic-306a01b4-20260420"
       };
       internals.overrideHookState = overrideHookState;
       internals.overrideHookStateDeletePath = overrideHookStateDeletePath;
@@ -20472,7 +20472,7 @@ __DEV__ &&
     exports.Shape = Shape;
     exports.Surface = Surface;
     exports.Text = Text;
-    exports.version = "19.3.0-www-classic-bc249804-20260417";
+    exports.version = "19.3.0-www-classic-306a01b4-20260420";
     "undefined" !== typeof __REACT_DEVTOOLS_GLOBAL_HOOK__ &&
       "function" ===
         typeof __REACT_DEVTOOLS_GLOBAL_HOOK__.registerInternalModuleStop &&

compiled/facebook-www/ReactART-dev.modern.js

@@ -20205,10 +20205,10 @@ __DEV__ &&
     (function () {
       var internals = {
         bundleType: 1,
-        version: "19.3.0-www-modern-bc249804-20260417",
+        version: "19.3.0-www-modern-306a01b4-20260420",
         rendererPackageName: "react-art",
         currentDispatcherRef: ReactSharedInternals,
-        reconcilerVersion: "19.3.0-www-modern-bc249804-20260417"
+        reconcilerVersion: "19.3.0-www-modern-306a01b4-20260420"
       };
       internals.overrideHookState = overrideHookState;
       internals.overrideHookStateDeletePath = overrideHookStateDeletePath;
@@ -20243,7 +20243,7 @@ __DEV__ &&
     exports.Shape = Shape;
     exports.Surface = Surface;
     exports.Text = Text;
-    exports.version = "19.3.0-www-modern-bc249804-20260417";
+    exports.version = "19.3.0-www-modern-306a01b4-20260420";
     "undefined" !== typeof __REACT_DEVTOOLS_GLOBAL_HOOK__ &&
       "function" ===
         typeof __REACT_DEVTOOLS_GLOBAL_HOOK__.registerInternalModuleStop &&