RFR: 8333729: C2 SuperWord: remove some @requires usages in test/hotspot/jtreg/compiler/loopopts/superword

[Emanuel Peter]

I'm removing as many `@requires` statements as possible. Generally, they just limit what tests can be executed where, and in most cases such limitations do not make much sense.

For example, tests should not be limited to `@requires vm.compiler2.enabled`, i.e. only run if C2 is available - we can also run the tests if GraalVM is available.

We should also not limit tests to `@requires vm.bits == "64"`, but rather limit the `@IR` rules with `applyIfPlatform = {"64-bit", "true"}`.

Similarly, we should not limit the platform for a run statement, but do that per `@IR` rule if necessary.

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Commit messages:
 - last file
 - Merge branch 'master' into JDK-8333729-superword-requires
 - JDK-8333729

Changes: https://git.openjdk.org/jdk/pull/19581/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=19581&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8333729
  Stats: 57 lines in 20 files changed: 20 ins; 32 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/19581.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19581/head:pull/19581

PR: https://git.openjdk.org/jdk/pull/19581