[RISCV] Add more tests for (and (srl x, C2), C1) that can be improved by using...

[RISCV] Add more tests for (and (srl x, C2), C1) that can be improved by using a pair of shifts. NFC

These tests have C1 as a shifted mask having C2 leading zeros and some
number of trailing zeros, C3. We can select this as
(slli (srli x, C2+C3), C3) or (slli (srliw x, C2+C3), C3).