RFR: 8302267: [jittester] Improve separation of test generation and execution

[Evgeny Nikitin]

Please review a set of improvements that should improve working with other fuzzing generators and usage of JitTesterDriver with tests generated not by the JITTester:

- Provide better separation of individual test generation from java file writing, compiling, executing, etc.;
- Introduce distinct Phases of the generation process (Generation, Compilation, GoldRun and VerificationRun);
- Extract JItTesterDriver headers generation so that it would be possible to provide other header generators;
- Introduce error tolerance to not get distracted by OOMEs, intrinsics missing in the compiled code, etc.;
- Make it possible to specify time limit for an individual test generation;
- Give better control over temp/workdir creation and cleaning;
- Unify external process running;
- Introduce UTF-8 support in external processes' output and human-readable escaping of it;

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Commit messages:
 - Remove tabs from a test to silence jcheck
 - 8302267: [jittester] Improve separation of test generation and execution

Changes: https://git.openjdk.org/jdk/pull/12527/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=12527&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8302267
  Stats: 1044 lines in 14 files changed: 834 ins; 161 del; 49 mod
  Patch: https://git.openjdk.org/jdk/pull/12527.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12527/head:pull/12527

PR: https://git.openjdk.org/jdk/pull/12527