[RISCV][test] Add new tests for add-mul optimization in the zba extension with SH*ADD

These tests will show the following optimization by future patches.

Rx + Ry * 18  => (SH1ADD (SH3ADD Rx, Rx), Ry)
Rx + Ry * 20  => (SH2ADD (SH2ADD Rx, Rx), Ry)
Rx + Ry * 24  => (SH3ADD (SH1ADD Rx, Rx), Ry)
Rx + Ry * 36  => (SH2ADD (SH3ADD Rx, Rx), Ry)
Rx + Ry * 40  => (SH3ADD (SH2ADD Rx, Rx), Ry)
Rx + Ry * 72  => (SH3ADD (SH3ADD Rx, Rx), Ry)
Rx * (3 << C) => (SLLI (SH1ADD Rx, Rx), C)
Rx * (5 << C) => (SLLI (SH2ADD Rx, Rx), C)
Rx * (9 << C) => (SLLI (SH3ADD Rx, Rx), C)

Reviewed By: craig.topper

Differential Revision: https://reviews.llvm.org/D104507