Transform vector SET{LE/ULT/ULE} -> SETLT and SET{GE/UGT/UGE} -> SETGT if possible

SETLT and SETGT can use `{v}pcmpgt` directly whereas the other SETCC
variants require some other instructions as well. On AVX512, which has
vector comparisons for all SETCC variants, this can still be
preferable if the destination is a vector. And if the destination is a
mask, its the same performance.

The transform for unsigned SETCC takes place if we know from
`KnownBits` that LHS/RHS have the same sign.

The transform for LE/GE -> LT/GT takes place if LHS/RHS is constant
and we can inc/dec all elements in the operand without overflowing
(both signed and unsigned).

Alive2 Links (on i8 so they don't timeout):
sge_s:   https://alive2.llvm.org/ce/z/rMPt9_
sge_s_2: https://alive2.llvm.org/ce/z/G74Mhs
sge_u:   https://alive2.llvm.org/ce/z/PTWARM
sge_u_2: https://alive2.llvm.org/ce/z/L9dsNn
sgt_s:   https://alive2.llvm.org/ce/z/q2CHEK
sgt_u:   https://alive2.llvm.org/ce/z/YPLnZ8
sle_s:   https://alive2.llvm.org/ce/z/HyYhQ_
sle_s_2: https://alive2.llvm.org/ce/z/ck6NkT
sle_u:   https://alive2.llvm.org/ce/z/tyF_wN
sle_u_2: https://alive2.llvm.org/ce/z/et8t98
slt_s:   https://alive2.llvm.org/ce/z/oCP43b
slt_u:   https://alive2.llvm.org/ce/z/EpLLPx
uge_s:   https://alive2.llvm.org/ce/z/rqSDwi
uge_s_2: https://alive2.llvm.org/ce/z/67UTXu
uge_u:   https://alive2.llvm.org/ce/z/yBNG9C
uge_u_2: https://alive2.llvm.org/ce/z/UhHYc_
ugt_s:   https://alive2.llvm.org/ce/z/tY9va4
ugt_u:   https://alive2.llvm.org/ce/z/F9zeAT
ule_s:   https://alive2.llvm.org/ce/z/1MNgka
ule_s_2: https://alive2.llvm.org/ce/z/oiS7Ls
ule_u:   https://alive2.llvm.org/ce/z/8DveC3
ule_u_2: https://alive2.llvm.org/ce/z/jGp2M7
ult_s:   https://alive2.llvm.org/ce/z/chzfwP
ult_u:   https://alive2.llvm.org/ce/z/Jj_JYu

Reviewed By: RKSimon

Differential Revision: https://reviews.llvm.org/D142254