Openjdk tests not ran in flagless configuration

[zzambers]

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.: #2708 (comment), #5245 (comment) ) or even to be SKIPPED. E.g. 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 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: #5316)