[LegalizeTypes][RISCV][WebAssembly] Expand ABS in PromoteIntRes_ABS if it will...

[LegalizeTypes][RISCV][WebAssembly] Expand ABS in PromoteIntRes_ABS if it will expand to sra+xor+sub later.

If we promote the ABS and then Expand in LegalizeDAG, then both the
sra and the xor will have their inputs sign extended. This generates
extra code on RISCV which lacks an i8 or i16 sign extend instructon.
If we expand during type legalization, then only the sra will get its
input sign extended. RISCV is able to combine this with the sra by
doing a shift left followed by an sra.

Reviewed By: RKSimon

Differential Revision: https://reviews.llvm.org/D121664