RFR: 8304016: Add BitMap find_last suite of functions [v2]

[Axel Boldt-Christmas]

On Sun, 19 Mar 2023 22:06:53 GMT, Kim Barrett <kbarrett at openjdk.org> wrote:

>> Please review this change that adds functions to BitMap for finding the last
>> set/clear bit in a range.
>> 
>> Testing:
>> mach5 tier1, including new gtesting for the new functions.
>
> Kim Barrett has updated the pull request incrementally with two additional commits since the last revision:
> 
>  - shrink find_first_bit_impl
>  - improve find_last_bit_impl

The rewrite made the algorithm more readable, imo.

At some point I would like to type up the `beg` and `end` so it is clear that it is a range with `[beg, end)`

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Marked as reviewed by aboldtch (Committer).

PR: https://git.openjdk.org/jdk/pull/12988