[WinEH] Start inserting state number stores for C++ EH

[WinEH] Start inserting state number stores for C++ EH

This moves all the state numbering code for C++ EH to WinEHPrepare so
that we can call it from the X86 state numbering IR pass that runs
before isel.

Now we just call the same state numbering machinery and insert a bunch
of stores. It also populates MachineModuleInfo with information about
the current function.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@238514 91177308-0d34-0410-b5e6-96231b3b80d8