feat: added recwave mvp, a PoC recommender system

[KivenChen]

Recwave is a PoC recommender system that utilizes the power of RisingWave MV.

https://singularity-data.quip.com/15kwA8raYjWC/WIP-Design-Recwave-a-PoC-Recommender-System

Current progress:

• User Simulator
  • [x] Generator: generate initial data for users and items
  • [x] Simulator RPC server
  • [x] Simulator
• Recommender
  • [x] Recommendation RPC server
  • [x] Recommender model
• Up and Running
  • [x] Docker build support