RFR: 8344071: Mark some jdk/jfr/event/oldobject test flagless until they fixed to support all GC

[Leonid Mesnik]

Tests
jdk/jfr/event/oldobject/TestObjectDescription.java
jdk/jfr/event/oldobject/TestClassLoaderLeak.java
fail with different GCs to get expected events.

They pass with G1 GC so I don't want to problemlist them.
However, they should test all GCs that support these events.

Removed ZGC, because I expect that is Generational and should be also supported.

The flagless should be removed when the main bugs are fixed.

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Commit messages:
 - Mark some jdk/jfr/event/oldobject test flagless until they fixed to support all GC

Changes: https://git.openjdk.org/jdk/pull/22050/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=22050&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8344071
  Stats: 7 lines in 2 files changed: 4 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/22050.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/22050/head:pull/22050

PR: https://git.openjdk.org/jdk/pull/22050