[llvm][DebugInfo][test] Add LLVM tests for Objective-C property debug-info (#165373)
The IR->DWARF pipeline was not properly tested before. This patch adds a
test to generate DWARF for various `DIObjCProperty` constructions.
This caught a couple of bugs:
1. The `DW_AT_APPLE_property_getter` and `DW_AT_APPLE_property_setter`
properties were emitted the wrong way around.
2. The `DW_TAG_member` ivars were not linking back to the property that
they back.
These will be fixed in follow-up patches.