Adds semantic session manager

[justin-cechmanek]

Here's the proposed class for LLM session management. It support recent or full conversation storage & retrieval, as well as relevance based conversation section retrieval.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 111 lines in your changes are missing coverage. Please review.

Project coverage is 83.07%. Comparing base (ce0f710) to head (3a117eb).

:exclamation: Current head 3a117eb differs from pull request most recent head 5d4f34b. Consider uploading reports for the commit 5d4f34b to get more accurate results

Files	Patch %	Lines
redisvl/extensions/session_manager/session.py	0.00%	109 Missing :warning:
redisvl/extensions/session_manager/__init__.py	0.00%	2 Missing :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #141      +/-   ##
==========================================
- Coverage   88.60%   83.07%   -5.54%     
==========================================
  Files          29       31       +2     
  Lines        1667     1778     +111     
==========================================
  Hits         1477     1477              
- Misses        190      301     +111     

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