[AArch64][BTI] Add BTI at EH entries. (#155308)
Mark EH landing pads as indirect-branch targets (BTI j) and treat WinEH
funclet entries as call-like (BTI c). Add lit tests for ELF and COFF.
Tests:
Adds lit tests: bti-ehpad.ll and wineh-bti-funclet.ll.
Fixes: #149267
Signed-off-by: Shashi Shankar <shashishankar1687@gmail.com>
