Add OMR port library to jit test environment

[ehsankianifar]

IBM Z (and maybe other platforms) need OMR port library to get the CPU version and determine capabilities. If the OMR port library does not exist, it default back to the minimum supported version which does not support many features and instructions. The OMR JIT unit tests harness initialize the OMR port library but doesn't add it to the test environment.As a result, many evaluators (e.g. vector opcodes) are not tested even though unit tests exist!
I tried adding the port library to the test environment but many tests on all platforms started to fail. I checked a few failures on Z and find some legit failures due to issues like test setup. To tackle this issue, I added another JitTest class with the OMR port library to have the option to drive tests from the new JitTest class. I used that in VectorTest on s390s and fixed the issue. It seem to be a good way to gradually migrate test without need to deal with a lot of changes and failures.
I opened a PR for the aforementioned changes #7912
I am opening this issue to discuss if we want this and if other platforms need this.
@0xdaryl @r30shah Please let me know your thoughts and tag anyone else that may be interested.

[hzongaro]

@Spencer-Comin had started to do something similar under pull request #7252 some time ago. I haven't looked closely at pull request #7912, but perhaps the two of you can work together to determine which ought to move forward or whether some combination of the two would be appropriate.

[ehsankianifar]

Thanks @hzongaro for sharing that PR. It is exactly what I want and will fix my issue if gets merged. @Spencer-Comin may I ask you to share your thoughts on this issue?