Add `impl From<[(K, V); N]> for Metadata` so array literals work with `with_metadata`

[alamb]

Is your feature request related to a problem or challenge?

• Found while testing upgrade of arrow in DataFusion: Update to arrow-rs main (arrow 60 pre-release testing) datafusion#24366
• Related to Use Metadata struct instead of HashMap<String, String> for metadata: Ordered; cheap to clone #10075

While updating DataFusion to arrow 60 I found that a very common pattern for attaching metadata to a Field or Schema no longer compiles. Before, with_metadata took a HashMap<String, String>, so an array literal converted via type inference:

Field::new("name", DataType::Utf8, false)
    .with_metadata([("some_key".to_string(), "some_value".to_string())].into())

Now that metadata parameters are generic (impl Into<Metadata>), the .into() target can no longer be inferred and this fails with error[E0283]: type annotations needed. The same applies to Default::default() and .collect() in metadata argument position.

Describe the solution you'd like

An array conversion such as:

impl<K: Into<String>, V: Into<String>, const N: usize> From<[(K, V); N]> for Metadata

so callers can pass the array directly, with no .into() and no owned String conversions:

Field::new("name", DataType::Utf8, false).with_metadata([("some_key", "some_value")])

Describe alternatives you've considered

Spelling out the type at each call site, e.g. Metadata::new().with("some_key", "some_value") or HashMap::from([...]); this works but required touching every call site.

Additional context

[Rich-T-kid]

I think this functionality already exist

arrow-rs/arrow-schema/src/metadata.rs

Line 196 in b5794fb

impl<K: Into<String>, V: Into<String>, const N: usize> From<[(K, V); N]> for Metadata {

fn create_field_with_metadata() {
        let field = Field::new("test", datatype::DataType::Utf8, false)
            .with_metadata([("key 1", "value 1")]);
        println!("field : {:?}", field)
    }

compiles fine