Loosen config field rust_input syntax with delimit ,

[dbsxdbsx]

Changes

Loose the strict syntax restriction for rust_input with delimit , in flutter_rust_bridge.yaml, mention here:
With this change, the below several styles of rust_input in flutter_rust_bridge.yaml are all supported with no generation error after running flutter_rust_bridge_codegen generate:

rust_input: module_b,module_a,
rust_input: module_a,
rust_input: module_a,module_b
rust_input: module_a, module_b
rust_input: module_a , module_b
rust_input: module_a ,module_b

Checklist

• An issue to be fixed by this PR is listed above.
• New tests are added to ensure new features are working. Please refer to this page to see how to add a test.
• ./frb_internal precommit --mode slow (or fast) is run (it internal runs code generator, does auto formatting, etc).
• If this PR adds/changes features, documentations (in the ./website folder) are updated.
• CI is passing. Please refer to this page to see how to solve a failed CI.

Remark for PR creator

• ./frb_internal --help shows utilities for development.
• If fzyzcjy does not reply for a few days, maybe he just did not see it, so please ping him.

[fzyzcjy]

LGTM! It would be great to add some simple unit test inside this file to test compute_rust_input_namespace_prefixes_raw, e.g.

#[cfg(test)]
mod tests {
    #[test]
    fn test_blahblah() {
        assert_eq!(compute_rust_input_namespace_prefixes_raw("one, two"), vec!["one", "two"]);
        ...
    }
}