[code-reflection] Integrated: Created optkl subproject containing tooling that does not depend on HAT

[Gary Frost]

I created optkl subproject. 

It contains a bunch of useful tooling that leverage babylon, but does not have depenencies on HAT itself. 

I plan to move the non HAT code builders down here as well as the iface mapper eventually.

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Commit messages:
 - Created optkl subproject containing  tooling that does not depend on HAT

Changes: https://git.openjdk.org/babylon/pull/758/files
  Webrev: https://webrevs.openjdk.org/?repo=babylon&pr=758&range=00
  Stats: 1675 lines in 122 files changed: 717 ins; 778 del; 180 mod
  Patch: https://git.openjdk.org/babylon/pull/758.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/758/head:pull/758

PR: https://git.openjdk.org/babylon/pull/758