[llvm] Adding IR2Vec as an analysis pass (PR #134004)

[S. VenkataKeerthy via llvm-commits]

svkeerthy wrote:

Currently, we have simplified the code by removing `IR2VecAnalysis` and directly using the `ir2vec::Embedder`. 

**Motivation**
* Our initial intention for IR2VecAnalysis was to leverage LLVM's analysis caching. However, recent experiments indicate that for our current use cases, recomputing embedding vectors is often cheaper than the overhead of caching them.
* This change also addresses earlier review feedback (related to simplifying how Embeddings objects are handled) by moving towards using the ir2vec::Embedder more directly as the primary container for embedding results.



https://github.com/llvm/llvm-project/pull/134004