Give FieldNamingStrategy the ability to return multiple String names

[mfriesen]

Purpose

This pull request enhances the FieldNamingStrategy in Gson to support returning multiple strings for a field name. This behavior aligns with the alternate names functionality provided by the @SerializedName annotation, allowing for greater flexibility in field mapping.

Description

The FieldNamingStrategy interface has been updated to allow implementations to return a list of potential field name mappings. This allows deserialization to succeed if any of the alternate names are present in the JSON data.

The changes include is to modifying the FieldNamingStrategy interface to support returning a collection of names. This allows the FieldNamingStrategy interface to behave like the @SerializedName annotation.

Checklist

• [ X] New code follows the Google Java Style Guide
  This is automatically checked by mvn verify, but can also be checked on its own using mvn spotless:check.
  Style violations can be fixed using mvn spotless:apply; this can be done in a separate commit to verify that it did not cause undesired changes.
• [X ] If necessary, new public API validates arguments, for example rejects null
• [X ] New public API has Javadoc
  • [ X] Javadoc uses @since $next-version$
    ($next-version$ is a special placeholder which is automatically replaced during release)
• [ X] If necessary, new unit tests have been added
  • [ X] Assertions in unit tests use Truth, see existing tests
  • [X ] No JUnit 3 features are used (such as extending class TestCase)
  • [X ] If this pull request fixes a bug, a new test was added for a situation which failed previously and is now fixed
• [X ] mvn clean verify javadoc:jar passes without errors