[LLDB][RISCV] Add more instruction decode and execute for EmulateInstructionRISCV

[LLDB][RISCV] Add more instruction decode and execute for EmulateInstructionRISCV

Add:
- most of instructions from RVI base instructions set.
- some instruction decode tests from objdump.

Further work:
- implement riscv imac extension.

Reviewed By: DavidSpickett

Differential Revision: https://reviews.llvm.org/D132789