[llvm] [RISCV][NFC] Move Zawrs implementation to RISCVInstrInfoZawrs.td (PR #76940)

[Wang Pengcheng via llvm-commits]

wangpc-pp wrote:

> > LGTM. I think it's not necessarily the case that every extension should have it's own file
> 
> I agree. Adding a file for every extension doesn't scale well if we keep adding extensions at the rate we are.

What about adding it to `RISCVInstrInfoZa.td`? We will have `Zabha` (https://github.com/riscv/riscv-zabha) and may have `Zalasr` (https://github.com/mehnadnerd/riscv-zalasr) later. 

And what is the policy? Should we put all (or these simple ones) `Zi*` extensions into `RISCVInstrInfoZi.td` for example? We already have `RISCVInstrInfoZb.td` and `RISCVInstrInfoZc.td`.

https://github.com/llvm/llvm-project/pull/76940