[hal] concurrent: expose full concurrent APIs.

[XuGuohui]

Expose the rest of concurrent HAL APIs.

Completeness

• User is totes amazing for contributing!
• Contributor has signed CLA (Info here)
• Problem and Solution clearly stated
• Run unit/integration/application tests on device
• Added documentation
• Added to CHANGELOG.md after merging (add links to docs and issues)

[eberseth]

Please add conditional variable support as well

[avtolstoy]

@eberseth Conditional variable implementation is broken. We've previously agreed that we are not going to expose them. If we do require this feature for other work, we should prioritize changing the implementation.

We can always add the support in a separate PR.

[eberseth]

Okay, we'll use an alternate implementation.

[avtolstoy]

@eberseth Alternate implementation within concurrent HAL or outside of it?

[eberseth]

Perhaps copying out the cv implementation into user space versus using a standard library.

[eberseth]

Reviewed