Product Recommendation Demo Naming Improvement

Current Product Recommendation Demo naming uses different style and anchor name is meaningless.
Improvement:
1. follow snake style in all entity names: `userProfileData` to `user_profile_data`
2. change anchor name to more meaningful words: e.g. `user_profile_anchor`
3. remove `feature` prefix of all features as its redundant.
4. summarize a `sample notebook style standard` with above rules