RFR: 8333729: C2 SuperWord: remove some @requires usages in test/hotspot/jtreg/compiler/loopopts/superword [v4]

[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.
> 
> Update: I had to add some extra `-XX:+IgnoreUnrecognizedVMOptions`, so that the C2 flags do not make the VM crash if C2 is not available. I ran all the relevant tests on a build without C2, see discussion in the thread below.

Emanuel Peter has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains six additional commits since the last revision:

 - Merge branch 'master' into JDK-8333729-superword-requires
 - fix some more tests
 - Merge branch 'master' into JDK-8333729-superword-requires
 - last file
 - Merge branch 'master' into JDK-8333729-superword-requires
 - JDK-8333729

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/19581/files
  - new: https://git.openjdk.org/jdk/pull/19581/files/7b54425b..52859f80

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=19581&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=19581&range=02-03

  Stats: 207 lines in 14 files changed: 153 ins; 18 del; 36 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