feat: Added Hybrid Search Config and Tests [1/N]

[vishwarajanand]

Adds configs and tests for Hybrid Search based on TSV + Vector Search

Other PRs:

• [1/N] feat: Added Hybrid Search Config and Tests [1/N] #211
• [2/N] feat: create hybrid search capable vector store table [2/N] vishwarajanand/langchain-postgres#1
• [3/N] feat: adds hybrid search for async VS interface [3/N] vishwarajanand/langchain-postgres#2
• [4/N] feat: adds hybrid search for sync VS interface [4/N] vishwarajanand/langchain-postgres#3

TODO:

Add documentation in a followup PR, ref for comment

[dishaprakash]

Should we also expose the config publicly (in the init)?