[llvm] [IR] Implementation and lowering of bitinsert and bitextract (PR #200605)

[Antonio Frighetto via llvm-commits]

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antoniofrighetto wrote:

```suggestion
      %result = bitextract i8, b32 %src, i32 24 ; Extract the 8 most-significant bits (bits [24..31]) of %src and return an 8-bit integer
```

https://github.com/llvm/llvm-project/pull/200605