DebugInfo: Emit only one kind of accelerated access/name table

Currently to opt in to debug_names in DWARFv5, the IR must contain
'nameTableKind: Default' which also enables debug_pubnames.

Instead, only allow one of {debug_names, apple_names, debug_pubnames,
debug_gnu_pubnames}.

nameTableKind: Default gives debug_names in DWARFv5 and greater,
debug_pubnames in v4 and earlier - and apple_names when tuning for lldb
on MachO.
nameTableKind: GNU always gives gnu_pubnames

llvm-svn: 358931