[GISel][RISCV] Legalize G_CONSTANT_FOLD_BARRIER (#89960)

This patch supports `G_CONSTANT_FOLD_BARRIER` on RISCV to generate the
following inst seq without crash:
```
define i64 @xor_and_i64(i64 %x) {
entry:
  %y = and i64 %x, 16383
  %z = xor i64 %y, 16368
  ret i64 %z
}
```