feat(search): Add HNSW encoding index & search/insertion algorithm

[Beihao-Zhou]

Implement Proposal at #2316

Todo for this PR

• [x] Error handling, common utility refactor
• [x] Split into header and implementation files
• [ ] Unit test for functionsSearchLayer and InsertVectorEntry
• [ ] Implement vector deletion

Future steps

• Add the plan operator and the corresponding executor
• Add expression node (i.e. SQL/RediSearch parsers) for vector search
• Modify some passes (eg. index_selection) to convert the expression node to plan operator