Fix LoopVectorizer profcheck failures

[mtrofin]

LV is actively worked on and tests are actively added, so disabling the whole test sub-directory until we get to it (==LV) and address profile propagation.

[fhahn]

Could you add an IR function showing the issue or add instructions how to reproduce?

[mtrofin]

To repro (see also RFC comment or profcheck bot)

cmake -GNinja ../llvm \
-DCMAKE_BUILD_TYPE=Release \
-DLLVM_ENABLE_ASSERTIONS=On \
-DCMAKE_EXPORT_COMPILE_COMMANDS=On \
-DLLVM_ENABLE_LLD=On \
-DLLVM_LIT_ARGS="--exclude-xfail" \
-DLLVM_ENABLE_PROFCHECK=On

ninja check-llvm