Reland "[lldb][MachO][NFC] Extract ObjC metadata symbol parsing into helper function" (#161655)
This reverts `5a80fb9177e3c831c9c574400a13d77393397f2a`. The original
change got reverted because of failing tests on macOS.
The issue was that I changed the scope of setting `type =
eSymbolTypeData` during the cleanup. This patch relands the original
patch but doesn't change the `else` branch to an `else if` branch.
Tested that macOS test-suite passes.