[llvm] [SandboxIR] Implemented isVolatile() for LoadInst (PR #100717)

[via llvm-commits]

vporpo wrote:

> should i include the body of the function too or will the function header alone suffice for now?
I think you should include the body too + test it. 
The best way to implement this is probably to add the `isVolatile` argument to the existing create() functions, then add new create() functions that look just like the existing ones (without the `isVolatile` argument) and in their bodies call the ones with the argument but set it to false.

https://github.com/llvm/llvm-project/pull/100717