[lldb] Add issue no to xfail decorators in TestGetBaseName (#155939)
TestGetBaseName.py is currently marked as an expected failure on Windows
because SBFunction::GetBaseName() and SBSymbol::GetBaseName() don’t yet
handle MSVC-style mangling.
This patch updates the @expectedFailureAll decorator to include a
reference to https://github.com/llvm/llvm-project/issues/156861