[clang] Add missing LinkageSpec case to getCursorKindForDecl (#72401)

The LinkageSpec case was omitted, and there is a declared CXCursor_Kind
for it. Adapt the testsuite drivers to print mangled names for
declarations with extern linkage. Also update the test baseline for the
recursive-cxx-member-calls.cpp test.

Co-authored-by: Matthieu Eyraud <eyraud@adacore.com>