ValueSource Has Generic Typing Issues [LUCENE-9255]

ValueSource uses a bunch of weakly typed members which raises compiler issues. We need to fix this in ValueSource and all of its subclasses.

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Migrated from [LUCENE-9255](https://issues.apache.org/jira/browse/LUCENE-9255) by Atri Sharma (@atris), updated Apr 27 2020

Start by locating ValueSource and enumerating all of its subclasses, then inspect the compiler diagnostics caused by their weakly typed members. The issue is complete when ValueSource and every subclass use appropriate generic types without compiler warnings or errors; no specific test or file path is provided, so the relevant test entry points must be found in the repository.

Written by the indexing model from the issue text.