RFR: 8252219: C2: Randomize IGVN worklist for stress testing [v8]

[Roberto Castaneda Lozano]

> Add `StressIGVN` option to let C2 randomize IGVN worklist order. When enabled, the worklist is shuffled before each
> main run of the IGVN loop. Also add `GenerateStressSeed` and `StressSeed=N` options to randomly generate or specify the
> seed. In either case, the seed is logged if `LogCompilation` is enabled. The new options are declared as
> production+diagnostic for consistency with the existing `StressLCM` and `StressGCM` options.

Roberto Castaneda Lozano has updated the pull request with a new target base due to a merge or a rebase. The pull
request now contains 14 commits:

 - Merge master
 - Add missing @requires annotation to test case
 - Empty commit to trigger jcheck after updating GitHub user name
 - Generate random seed if 'StressSeed' is unset
 - Use generic swap() for shuffling
 - Add basic sanity test for stress IGVN options
 - Fix typo
 - Move shuffle() to PhaseIterGVN
 - Define 'StressSeed' option as 'uint' rather than 'uintx'
 - Apply minor rearrangements to simplify the patch
 - ... and 4 more: https://git.openjdk.java.net/jdk/compare/37b70282...c2c31c3e

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Changes: https://git.openjdk.java.net/jdk/pull/242/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=242&range=07
  Stats: 229 lines in 10 files changed: 224 ins; 0 del; 5 mod
  Patch: https://git.openjdk.java.net/jdk/pull/242.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/242/head:pull/242

PR: https://git.openjdk.java.net/jdk/pull/242