RFR: 8281631: HashMap copy constructor and putAll can over-allocate table [v25]

[liach]

On Fri, 4 Mar 2022 17:30:48 GMT, XenoAmess <duke at openjdk.java.net> wrote:

>> 8281631: HashMap copy constructor and putAll can over-allocate table
>
> XenoAmess has updated the pull request incrementally with one additional commit since the last revision:
> 
>   refine test

nitpick for the test code: for better performance, move method handle and var handle to static final fields so the jvm can run faster

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PR: https://git.openjdk.java.net/jdk/pull/7431