CodeGenPrepare: Convert most tests to opaque pointers

NVPTX/dont-introduce-addrspacecast.ll required manually removing a check for
a bitcast.

AArch64/combine-address-mode.ll required rerunning update_test_checks

Mips required some manual updates due to a CHECK-NEXT coming after a
deleted bitcast.

ARM/sink-addrmode.ll needed one small manual fix.

Excludes one X86 function which needs more attention.