RFR: 8281467: Allow larger OptoLoopAlignment and CodeEntryAlignment

[Aleksey Shipilev]

I am following up on the performance issue where the culprit seems to be the too low `OptoLoopAlignment`. To perform better experiments, I suggest allowing larger alignments.

Note that we cannot make `OptoLoopAlignment` larger than `CodeEntryAlignment`, because nmethod copy would break it, see assert in `MacroAssembler::align`. See [JDK-8273459](https://bugs.openjdk.java.net/browse/JDK-8273459) for latest discussion about it. So `CodeEntryAlignment` needs to be configurable as well.

The default values for options are different per platform, so tests are x86_64 specific.

No default value is changed, this only unblocks experiments.

Additional testing:
 - [x] New tests on Linux x86_64 fastdebug
 - [x] New tests on Linux x86_64 release

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Commit messages:
 - Fix

Changes: https://git.openjdk.java.net/jdk/pull/7388/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=7388&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8281467
  Stats: 178 lines in 4 files changed: 176 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7388.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7388/head:pull/7388

PR: https://git.openjdk.java.net/jdk/pull/7388