FSMemoryStore isFile/isDirectory checks break when FFI package is loaded

[MariusDoe]

These two methods expect an Association:

squeak-filesystem/src/FS-Memory.package/FSMemoryStore.class/instance/basicIsFile..st

Lines 2 to 3 in 74acb4a

	basicIsFile: association
	^ association value isDictionary not

squeak-filesystem/src/FS-Memory.package/FSMemoryStore.class/instance/basicIsDirectory..st

Lines 2 to 3 in 74acb4a

	basicIsDirectory: association
	^ association value isDictionary

But in case they receive a ByteArray or Dictionary, Object>>value comes to the rescue and prevents this code from breaking.
However, FFI-Kernel adds this method on RawBitsArray (from which ByteArray inherits):

value
	^self at: 1

This breaks the two methods above when they are given a ByteArray.
This actually happens quite often, e. g.:

squeak-filesystem/src/FS-Memory.package/FSMemoryStore.class/instance/createFile..st

Lines 2 to 8 in 74acb4a

	createFile: aPath
	^ self
	nodeAt: aPath parent
	ifPresent: [ :dict |
	(self basicIsDirectory: dict)
	ifTrue: [ dict at: aPath basename put: ByteArray new ] ]
	ifAbsent: [ self signalDirectoryDoesNotExist: aPath parent ]

Note that the other implementations usually return an "entry" (name -> node) rather than a plain "node" from nodeAt:ifPresent:ifAbsent:, contrary to what the name might suggest.

I see a few ways to fix this, in increasing order of (estimated) amount of code changed:

1. Add something like fs[Memory]Node to Association, ByteArray, and Dictionary and send that instead of value in basicIs{File,Directory}:
2. Add something like fsIs[Memory]{File,Directory} to Assocation, ByteArray, and Dictionary
3. Wrap the plain nodes in a temporary Association before passing them to basicIs{File,Directory}:, as in self basicIsDirectory: '' -> dict. Although that feels the most ugly to me.
4. Change nodeAt:ifPresent:ifAbsent: to return the entry (Association) instead of the plain node (ByteArray/Dictionary) and adjust its senders, which can then pass the Assocation to basicIs{File,Directory}:. AFAICT, that would align its behavior more with the other implementations of it. Note that this would require us to give a name to the root node, which could be empty, i. e. self root = ('' -> Dictionary new), and we have to decide whether to store this Association or create it temporarily when needed.

[LinqLover]

5. In basicIs{File,Directory}, check whether association isAssociation (and probably give the argument a better name) and only if yes send value to it?