RFR: 8275104: IR framework does not handle client VM builds correctly

[Christian Hagedorn]

While the IR framework is primarily used for C2 IR verification, it should also work with client VM builds. There are currently some problems which are fixed with this patch:

- The IR framework currently only bails out of IR matching if C2 is excluded by command line flags. However, when running an IR JTreg test with a client VM build, IR matching fails when not specifically adding `@requires vm.compiler2.enabled` to exclude the test.
- `@Test` and `@ForceCompile` do not work correctly and throw an exception due to an incompatible compilation level selection without C2.
- Some internal framework tests fail (the fix also improves `TestDIgnoreCompilerControls` in general).

Testing:

- Standard tier testing
- Testing internal framework tests with standard build (tiered), client VM (without C2) and server VM build (without C1)

Thanks,
Christian

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Commit messages:
 - 8275104: IR framework does not handle client VM builds correctly

Changes: https://git.openjdk.java.net/jdk/pull/6037/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6037&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8275104
  Stats: 79 lines in 8 files changed: 30 ins; 18 del; 31 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6037.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6037/head:pull/6037

PR: https://git.openjdk.java.net/jdk/pull/6037