[rocm-libraries] ROCm/rocm-libraries#6900 (commit 28608c2)

[CK] Fix and expand CK's commit records in version.h (#6900)

## Motivation

In `version.h` of a CK installation `CK_COMMIT_ID` would be empty for
out-of-source builds.
Additionally, if it worked, it would show the parent repo's
(`rocm-libraries`) commit.

## Technical Details

Dropped "required" constraint so "unknown" string becomes a graceful
option.

Changed process of determining the CK commit, now uses
`WORKING_DIRECTORY`.
Thus, `CK_COMMIT_ID` holds only the last CK-relevant commit.

Added `CK_PARENT_COMMIT_ID` which holds the parent's, e.g.
`rocm-libraries`, commit.
This can be the same as `CK_COMMIT_ID`, or not even applicable,
depending on the scenario.

## Test Plan

Ran CMake configuration and installation of CK to verify happy path.

## Test Result

Commit SHA's showed the expected values depending on the repo state.

## Submission Checklist

- [ x ] Look over the contributing guidelines at
https://github.com/ROCm/ROCm/blob/develop/CONTRIBUTING.md#pull-requests.