Support linear memory in RedisMemory

[justin-cechmanek]

Why are these changes needed?

Current RedisMemory always uses semantic similarity to return memories. This PR adds support to optionally use purely sequential memory via config settings, or query sequentially on the default semantic RedisMemory.

Related issue number

None

Checks

• I've included any doc changes needed for https://microsoft.github.io/autogen/. See https://github.com/microsoft/autogen/blob/main/CONTRIBUTING.md to build and test documentation locally.
• I've added tests (if relevant) corresponding to the changes introduced in this PR.
• I've made sure all auto checks have passed.

[codecov]

Codecov Report

❌ Patch coverage is 57.69231% with 11 lines in your changes missing coverage. Please review.
✅ Project coverage is 80.99%. Comparing base (7fbf8ab) to head (93f6977).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...-ext/src/autogen_ext/memory/redis/_redis_memory.py	57.69%	11 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6972      +/-   ##
==========================================
- Coverage   80.99%   80.99%   -0.01%     
==========================================
  Files         237      237              
  Lines       18186    18196      +10     
==========================================
+ Hits        14730    14737       +7     
- Misses       3456     3459       +3     

Flag	Coverage Δ
unittests	80.99% <57.69%> (-0.01%)	⬇️

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[justin-cechmanek]

The codecov metrics seem to be off. Several sections are marked as uncovered, but certainly are being executed in the tests.