Add Strands Agent Session Manager

[yaron2]

Adds the ability to store Strands Agents session state with Dapr.

[codecov]

Codecov Report

❌ Patch coverage is 85.23985% with 40 lines in your changes missing coverage. Please review.
✅ Project coverage is 86.97%. Comparing base (bffb749) to head (fee12a5).
⚠️ Report is 56 commits behind head on main.

Files with missing lines	Patch %	Lines
...t-strands/dapr/ext/strands/dapr_session_manager.py	79.47%	39 Missing ⚠️
ext/dapr-ext-strands/tests/test_session_manager.py	98.73%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #872      +/-   ##
==========================================
+ Coverage   86.63%   86.97%   +0.34%     
==========================================
  Files          84      103      +19     
  Lines        4473     6900    +2427     
==========================================
+ Hits         3875     6001    +2126     
- Misses        598      899     +301     

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