Re-apply "[ORC][LLJIT] Move enable-debugger-support utility out of..."

This re-applies e1a5bb59, which was reverted in e5f169f9 due to LSan
failures on some bots (see https://github.com/llvm/llvm-project/issues/67586).
The LSan failures were not caused by this patch (just exposed by it), so LSan
was disabled for the failing test in 47625fea. This should be safe to
re-land now.