[X86] -fpatchable-function-entry=N,0: place patch label after ENDBR{32,64}

Similar to D73680 (AArch64 BTI).

A local linkage function whose address is not taken does not need ENDBR32/ENDBR64. Placing the patch label after ENDBR32/ENDBR64 has the advantage that code does not need to differentiate whether the function has an initial ENDBR.

Also, add 32-bit tests and test that .cfi_startproc is at the function
entry. The line information has a general implementation and is tested
by AArch64/patchable-function-entry-empty.mir

Reviewed By: nickdesaulniers

Differential Revision: https://reviews.llvm.org/D73760