[clang] [CIR] vector-saturating-left vqshl_*/ vqshlu_* (PR #203168)

[Kartik Ohlan via cfe-commits]

Ko496-glitch wrote:

@banach-space  i forgot to close https://github.com/llvm/llvm-project/pull/202508, i believe it was my disk sitiing on wrong version and giving me trouble even i did git fetch upstream. 


I used AI for the error fix since locally for me it was already passing all the test cases ? (this is before this change)
-- Testing: 1 tests, 1 workers --
```
PASS: Clang :: CodeGen/AArch64/neon/intrinsics.c (1 of 1)

Testing Time: 0.57s

Total Discovered Tests: 1
  Passed: 1 (100.00%) 
```

once i get time this weekend i will look more into this as i have to understand how this result wrong IR codegen and how the fix makes sense. 

https://github.com/llvm/llvm-project/pull/203168