RFR: 8356783: CompilerTask hot_method is redundant

[Vladimir Kozlov]

On Mon, 12 May 2025 14:02:43 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> This gave me some grief when implementing [JDK-8231269](https://bugs.openjdk.org/browse/JDK-8231269). From the initializations, it looks to me that `CompilerTask::hot_method()` is either `method()` or `nullptr`. In both cases, we do nothing special. So tracking `hot_method` is redundant, and can be purged. This improves performance a little, since it avoids extra handle-izing across compiler code, and of course it simplifies coding as well.
> 
> Additional testing:
>  - [x] Linux x86_64 server fastdebug, `compiler/`
>  - [ ]  Linux x86_64 server fastdebug, `all`

There was time when we compiled caller instead of method which triggers compilation (`StackWalkCompPolicy`). It was removed in JDK 13 [JDK-8216360](https://bugs.openjdk.org/browse/JDK-8216360)

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Marked as reviewed by kvn (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/25185#pullrequestreview-2833911401