Openjdk tests not ran in flagless configuration

As far as I know openjdk targets now usually run in 2 configurations:
- with compressed references explicitly enabled using `-XX:+UseCompressedOops`
- with compressed references explicitly disabled using `-XX:-UseCompressedOops`

There are some issues with that. Additional flags may cause some tests to misbehave (e.g.: https://github.com/adoptium/aqa-tests/issues/2708#issuecomment-1451869869, https://github.com/adoptium/aqa-tests/issues/5245#issuecomment-2096594183 ) or even to be **SKIPPED**. E.g. [JDK-8246494](https://bugs.openjdk.org/browse/JDK-8246494) (JDK 11+) introduced `@required vm.flagless` property, to only run test in configuration, without additional vm flags (`-X`, `-XX`). There are [quite a lot of tests](https://github.com/search?q=repo%3Aopenjdk%2Fjdk+vm.flagless&type=code) using `@required vm.flagless` (mostly in hotspot tests, but also in jdk tests). These tests are currently being skipped.

I think there should be run in flagless configuration (especially hotspot). (Or maybe only selected set of tests could be ran with explicit compressed oops setting?)

Actually there are tests for hotspot, which test compressed references and compressed class pointers (on/off). (However on 11+, most are not ran, see: https://github.com/adoptium/aqa-tests/issues/5316)

Start by reviewing the OpenJDK test configurations in aqa-tests, focusing on hotspot tests and the `vm.flagless` requirements described in the issue. Compare runs with explicit compressed-reference flags against a flagless configuration, then verify that applicable tests are no longer skipped and that compressed-reference coverage remains intact.

Written by the indexing model from the issue text.