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).
46e848a23b