Hide 'align' instruction behind jmp (#60787)

Hide 'align' instruction behind jmp (#60787)

* Hide align behind a jmp

fix the alignBytesRemoved

Some fixes and working model

Some fixes and redesign

Some more fixes

more fixes

fix

Add the check  for fgFirstBB

misc changes

code cleanup + JitHideAlignBehindJmp switch

validatePadding only if align are before the loop IG

More cleanup, remove commented code

jit format

* Fix a problem where curIG==0 and loop might be emitted in curIG, adjust the targetIG to prevIG

Add IGF_REMOVED_ALIGN flag for special scenarios

* Add stress mode to emit int3 for xarch

* Add stress mode to emit bkpt for arm64

* Add a loop align instruction placement phase

* review comments

* Change from unsigned short to unsigned

* review comments around cleanup

* emitForceNewIG

* Remove emitPrevIG

* Revert change to forceNewIG for align instruction

* Use loopAlignCandidates

* Use loopHeadIG reference

* jit format

* Remove unneeded method

* Misc changes

* Review feedback

* Do not include align behind Jmp in PerfScore calculation

* jit format and fix a bug

* fix the loopCandidates == 0 scenario

* Add unmarkLoopAlign(), add check for fgFirstBB

* merge conflict fix

* Add missing }

* Grammar nit

Co-authored-by: Bruce Forstall <brucefo@microsoft.com>
Co-authored-by: Bruce Forstall <brucefo@microsoft.com>