Add overflow flags support to the following ops:
* `arith.addi`
* `arith.subi`
* `arith.muli`
Example of new syntax:
```
%res = arith.addi %arg1, %arg2 overflow<nsw> : i64
```
Similar to existing LLVM dialect syntax
```
%res = llvm.add %arg1, %arg2 overflow<nsw> : i64
```
Tablegen canonicalization patterns updated to always drop flags, proper
support with tests will be added later.
Updated LLVMIR translation as part of this commit as it currenly written
in a way that it will crash when new attributes added to arith ops
otherwise.
Discussion
https://discourse.llvm.org/t/rfc-integer-overflow-flags-support-in-arith-dialect/76025
---------
Co-authored-by: Yi Wu <yi.wu2@arm.com>
a7262d2d9b