Add DisposableAnalyzer foreach tests and fix enumerator false positives

[google-labs-jules]

This change addresses the need for verifying that DisposableAnalyzer does not report false positives when foreach loops are used. In C#, the compiler automatically handles the disposal of enumerators in foreach blocks. The analyzer now ignores any type whose name ends with "Enumerator", which covers IEnumerator, IEnumerator<T>, and concrete enumerator implementations.

Added tests cover:

• Custom IEnumerable implementation.
• foreach on a method returning IEnumerable.
• foreach on List<float>.
• foreach on string[].

All tests passed successfully.

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PR created automatically by Jules for task 3140017500505977013 started by @sator-imaging

[google-labs-jules]

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