[llvm] [Exegesis] Add the ability to dry-run the measurement phase (PR #121991)

[Min-Yih Hsu via llvm-commits]

mshockwave wrote:

> > It is useful when we want to test some parts of the code between the assemble-measured-code and measure phase without actually running on native platforms.
> 
> Could you give some examples of what you're talking about here? Debugging the benchmark runners?

Actually #121993 is a good example (and why it's stacked on top of this PR): without `dry-run-measurement`, we cannot test the deserialization without actually executing the snippet.

https://github.com/llvm/llvm-project/pull/121991