RFR: JDK-8310861: Improve location reporting for javac serial lint warnings [v2]

[Jan Lahoda]

On Mon, 26 Jun 2023 01:30:15 GMT, Joe Darcy <darcy at openjdk.org> wrote:

>> For a subset of the expanded serial lint warnings ([JDK-8202056](https://bugs.openjdk.org/browse/JDK-8202056), [JDK-8160675](https://bugs.openjdk.org/browse/JDK-8160675)), javac uses the location of the enclosing type rather than the method or field in question.
>> 
>> This PR addresses this by using the idiom of finding the method/field's tree within the type tree being checked.
>> 
>> All langtools regression tests pass when run locally; the intention is to backport this fix to JDK 21 as well.
>
> Joe Darcy has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Cover additional case.

Looks good to me.

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Marked as reviewed by jlahoda (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/14644#pullrequestreview-1498531655