[crac] RFR: 8371549: [CRaC] Implement C/R in Selector on non-Linux [v2]

[Radim Vansa]

> Historically we have an extensive set of tests for java.nio.channels.Selector. However this runs only on Linux (using CRIU) rather than being platform agnostic and tested on all platforms. On Linux, it does not exercise PollSelectorImpl (this can be preferred using a system property) either - just the default EpollSelectorImpl.
> 
> This PR enables testing on all available Selector implementations, cleans up the implementation of those tests and introduces the C/R implementations.

Radim Vansa has updated the pull request incrementally with one additional commit since the last revision:

  Set FD value on Windows, too

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Changes:
  - all: https://git.openjdk.org/crac/pull/276/files
  - new: https://git.openjdk.org/crac/pull/276/files/69fead7d..8fff09d5

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=crac&pr=276&range=01
 - incr: https://webrevs.openjdk.org/?repo=crac&pr=276&range=00-01

  Stats: 10 lines in 1 file changed: 7 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/crac/pull/276.diff
  Fetch: git fetch https://git.openjdk.org/crac.git pull/276/head:pull/276

PR: https://git.openjdk.org/crac/pull/276