Follow-up to https://github.com/llvm/llvm-project/pull/96932
Adds XFAILed test where LLDB incorrectly infers the alignment of a
derived class whose bases are overlapping due to [[no_unique_address]].
Specifically, the `InferAlignment` code-path of the
`ItaniumRecordLayoutBuilder` assumes that overlapping base offsets imply
a packed structure and thus sets alignment to 1. See discussion in
https://github.com/llvm/llvm-project/pull/93809.
Also adds test where LLDB correctly infers an alignment of `1` when a
packed base class is overlapping with other bases.
Lastly, there were a couple of `alignof` inconsistencies which I
encapsulated in an XFAIL-ed `packed-alignof.cpp`.
Adds test that checks whether LLDB correctly infers the
alignment of packed structures. Specifically, the
`InferAlignment` code-path of the `ItaniumRecordLayoutBuilder`
where it assumes that overlapping field offsets imply a
packed structure and thus sets alignment to `1`. See discussion
in https://github.com/llvm/llvm-project/pull/93809.
While here, also added a test-case where we check alignment of
a class whose base has an explicit `DW_AT_alignment
(those don't get transitively propagated in DWARF, but don't seem
like a problem for LLDB).
Lastly, also added an XFAIL-ed tests where the aforementioned
`InferAlignment` kicks in for overlapping fields (but in this
case incorrectly since the structure isn't actually packed).
