Revert "[clang] Refactor AST printing tests to share more infrastructure"

This reverts commit 20176bc7 as some
versions of GCC do not seem to handle the new code very well. They
complain about:

/tmp/ccqUQZyw.s: Assembler messages:
/tmp/ccqUQZyw.s:1151: Error: symbol `_ZNSt14_Function_base13_Base_managerIN5clangUlPKNS1_4StmtEE2_EE10_M_managerERSt9_Any_dataRKS7_St18_Manager_operation' is already defined
/tmp/ccqUQZyw.s:11963: Error: symbol `_ZNSt17_Function_handlerIFbPKN5clang4StmtEENS0_UlS3_E2_EE9_M_invokeERKSt9_Any_dataOS3_' is already defined

This seems like it is some GCC issue, but multiple buildbots (and my
local machine) are all failing because of it.