[llvm] [MIR2Vec] Add embedder for machine instructions (PR #162161)

[S. VenkataKeerthy via llvm-commits]

svkeerthy wrote:

### Merge activity

* **Oct 21, 5:12 PM UTC**: A user started a stack merge that includes this pull request via [Graphite](https://app.graphite.dev/github/pr/llvm/llvm-project/162161).


https://github.com/llvm/llvm-project/pull/162161