Seperate Crimson flavors to crimson-debug/release

Seperate Crimson flavors to crimson-debug/release
The following change would allow us to:

* Keep testing "Debug" builds (crimson-debug) by default.
* When crimson-only is used, crimson-release would also be built.
* `crimson-release` builds would be used in the weekly nightlies and on
  selected PR gatings (when crimson-debug is not enough).

Note: Once crimson-release is stable enough we could switch crimson-debug
      to actaully be of: "RelWithDebInfo + !NDEBUG + asserts" instead of "Debug".
      For now, let's keep it as Debug since we know it's stable.

Signed-off-by: Matan Breizman <mbreizma@redhat.com>