IR: Remove unnecessary TraitsClass typedef, NFC

No classes are specializing the symbol table traits, so no need to look
through a typedef for class API.  Make a few more functions private
since only SymbolTableListTraits should be using them.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@249476 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed