[Fix] Stack overflow in Redis Backend and RestrictPolicy couldn't be saved when using DE embedding layer.

[MoFHeka]

Description

Fix tmpDirPath with fixed size may cause stack overflow in Redis backend. The char size of the entered file path may exceed 1024. Fixes #405 Fix restrict_policy wasn't tracked when using Embedding layer. Fixes #385

Type of change

• [x] Bug fix
• [ ] New Tutorial
• [ ] Updated or additional documentation
• [ ] Additional Testing
• [ ] New Feature

Checklist:

• [x] I've properly formatted my code according to the guidelines
  • [x] By running yapf
  • [x] By running clang-format
• [x] This PR addresses an already submitted issue for TensorFlow Recommenders-Addons
• [x] I have made corresponding changes to the documentation
• [x] I have added tests that prove my fix is effective or that my feature works

How Has This Been Tested?

When using redis backend, enter a non-existent file path that is longer than 1024.