RFR: 8318480: Deprecate UseCounterDecay and remove CounterDecayMinIntervalLength [v3]

[David Holmes]

On Wed, 15 Nov 2023 19:24:51 GMT, Daniel Lundén <duke at openjdk.org> wrote:

>> This changeset deprecates the leftover (i.e., no longer used for anything) product compiler flag `UseCounterDecay` (requires CSR) and removes the leftover develop flag `CounterDecayMinIntervalLength`.
>> 
>> Changes:
>> - Deprecate `UseCounterDecay` in JDK 22, obsolete it in JDK 23, and expire it in JDK 24. The flag is, in fact, already obsolete, so I've also removed it from the source code (except for the definition in `globals.hpp` which must remain until obsoletion).
>> - Completely remove `CounterDecayMinIntervalLength`.
>> 
>> ### Testing
>> Platforms: windows-x64, linux-x64, linux-aarch64, macosx-x64, macosx-aarch64.
>> - `tier1`
>> - HotSpot parts of `tier2` and `tier3`
>
> Daniel Lundén has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Update copyright

As `UseCounterDecay` already does nothing there is no need to have a deprecation step - just go straight to obsoletion. The only difference to the user will be the message they see.

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PR Review: https://git.openjdk.org/jdk/pull/16673#pullrequestreview-1733590890