[crac] RFR: Resize ForkJoinPool and some concurrent data structures

[Ashutosh Mehra]

On Thu, 23 Mar 2023 16:10:44 GMT, Radim Vansa <duke at openjdk.org> wrote:

> Some parts of JDK expect that #cpus is constant; update those places after restore.

Reading up the discussion on [FJP::setParallelism](https://mail.openjdk.org/pipermail/crac-dev/2022-May/000229.html), it was suggested [here](https://mail.openjdk.org/pipermail/crac-dev/2022-May/000230.html) to have crac branch receiving updates from openjdk/jdk/master, and crac-17u from openjdk/jdk17u/master. 

If we go with that plan, then this PR can be targeted to crac-17u while the crac branch can make use of Doug's patch.
Although it would fragment the implementation across the two branches, but as long as they are providing the same functionality, I guess we can live with that. Does that make sense?

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PR Comment: https://git.openjdk.org/crac/pull/54#issuecomment-1483007502