[X86] Increase the number of instructions searched for isSafeToClobberEFLAGS in a couple places

Previously this function searched 4 instructions forwards or
backwards to determine if it was ok to clobber eflags.

This is called in 3 places: rematerialization, turning 2 operand
leas into adds or splitting 3 ops leas into an lea and add on some
CPU targets.

This patch increases the search limit to 10 instructions for
rematerialization and 2 operand lea to add. I've left the old
treshold for 3 ops lea spliting as that increases code size.

Fixes PR47024 and PR43014