RFR: 8287726: Fix JVMTI tests with "requires vm.continuations" after JDK-8287496

[Aleksey Shipilev]

[JDK-8287496](https://bugs.openjdk.java.net/browse/JDK-8287496) brought the alternative Loom implementation that can be used by ports as the fallback. That fallback does not support JVMTI entirely, so lots of tests fail. Some JVMTI is still supported, so cutting off at `@requires vm.jvmti` seems too broad. They should be predicated with `@requires vm.continuations` to be skipped when fallback is used.

This also allows reverting x86_32 problemlist exclusions, which serves a proof of concept that [JDK-8287496](https://bugs.openjdk.java.net/browse/JDK-8287496) indeed works.

Additional testing:
 - [x] Linux x86_32 fastdebug, `serviceability/jvmti` works, many tests skipped
 - [ ] Linux x86_64 fastdebug, `serviceability/jvmti` still works, with all current tests executing

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Commit messages:
 - Only trim down JVMTI tests from x86_32 problemlists
 - Fix

Changes: https://git.openjdk.java.net/jdk/pull/8990/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8990&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8287726
  Stats: 138 lines in 69 files changed: 69 ins; 69 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8990.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8990/head:pull/8990

PR: https://git.openjdk.java.net/jdk/pull/8990