Fix type lookup bug where wrong decl context was being used for a DIE. (#94846)

The function that calculated the declaration context for a DIE was incorrectly transparently traversing acrosss DW_TAG_subprogram dies when climbing the parent DIE chain. This meant that types defined in functions would appear to have the declaration context of anything above the function. I fixed the GetTypeLookupContextImpl(...) function in DWARFDIE.cpp to not transparently skip over functions, lexical blocks and inlined functions and compile and type units. Added a test to verify things are working.