RFR: 8274299: Make Method/Constructor/Field accessors @Stable

[Mandy Chung]

On Sat, 25 Sep 2021 10:15:11 GMT, Peter Levart <plevart at openjdk.org> wrote:

> This patch improves reflective access speed as shown by the included benchmarks:
> 
> https://jmh.morethan.io/?gists=902f4b43519c4f96c7abcd14cdc2d27d,ac490481e3001c710d75d6071c10b23a
> 
> ... and is also a prerequisite to make JEP 416 (Reimplement Core Reflection with Method Handle) perform better in some circumstances.

Adding to Peter's description - separating this patch from JEP 416 will give some bake time on this change of the existing core reflection implementation.  When JEP 416 is integrated, it will switch the new implementation and the changes in `*AccessorImpl` will not be exercised.   In addition, this will make the backport easier if desirable.

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PR: https://git.openjdk.java.net/jdk/pull/5694