[v2] add initial Command Buffers support

[pbalcer]

No description provided.

[pbalcer]

This is a rebased and cleaned up version of #2532. I didn't want to force push to that PR to preserve the old history on that branch.

[EwanC]

This PR doesn't relax UUR_KNOWN_FAILURE_ON(uur::LevelZeroV2{}); at https://github.com/oneapi-src/unified-runtime/blob/main/test/conformance/exp_command_buffer/fixtures.h#L58 in the base CTS class, is this intentional?

[lslusarczyk]

This PR doesn't relax UUR_KNOWN_FAILURE_ON(uur::LevelZeroV2{}); at https://github.com/oneapi-src/unified-runtime/blob/main/test/conformance/exp_command_buffer/fixtures.h#L58 in the base CTS class, is this intentional?

Good point. Let's postpone enabling tests to next PRs. I'd like this PR to be merged soon, to be able to work further in parallel on v2 graphs.

[lslusarczyk]

@Bensuo , @EwanC , @igchor ,
thank you for your comments. I've applied them. Please check if I've applied them correctly. Please resolve discussions which were applied correctly or please comment these discussions which you think need more work/discussion.

[EwanC]

LGTM as a first stage