RFR: 8253765: C2: Control randomization in StressLCM and StressGCM

Fri Oct 9 08:35:28 UTC 2020

Use the compilation-local seed in `StressLCM` and `StressGCM` rather than the global one. As a consequence, these
options use by default a fresh seed in every compilation, unless `StressSeed=N` is specified, in which case they behave
deterministically. Annotate tests that use `StressLCM` and `StressGCM` with the `stress` and `randomness` keys to
reflect this change in default behavior.

Tested on `tier1` and on all test cases that use `StressLCM` and `StressGCM` (10 times each).

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Commit messages:
 - 8253765: C2: Control randomization in StressLCM and StressGCM

Changes: https://git.openjdk.java.net/jdk/pull/572/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=572&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8253765
  Stats: 104 lines in 18 files changed: 90 ins; 0 del; 14 mod
  Patch: https://git.openjdk.java.net/jdk/pull/572.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/572/head:pull/572

PR: https://git.openjdk.java.net/jdk/pull/572