Re-land "[lldb] Make the API, Shell and Unit tests independent lit test suites"

The commit got reverted because the tests were being run twice because
of the overlapping test_exec_root. Pavel has since fixed that in
8248dd91d7f042893d4a605e98d19cb1b89a44d4.

GitOrigin-RevId: eb26afbafe8b6fb115aac7f5e7ba80edc32138ab
5 files changed