chore: e2e tests for metadata changes

[adarsh0728]

What this PR does / why we need it

Adds e2e tests for user metadata propagation from source to sink

• Source creates user metadata with group simple-source and adds txn-id key
• Transformer adds event-time to group event-time-group
• Map logs both groups: "Groups at mapper: [event-time-group simple-source]" and creates additional group map-group with map-key
• Sink logs all user metadata received

Related issues

Fixes #2980

Testing

Ran e2e tests locally make TestMonoVertexUserMetadataPropagation and make TestPipelineUserMetadataPropagation

Special notes for reviewers

Updated to latest numaflow-rs commit PR numaproj/numaflow-rs#151

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 79.81%. Comparing base (bd4b057) to head (e5d71c9).
⚠️ Report is 5 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3065      +/-   ##
==========================================
- Coverage   79.84%   79.81%   -0.03%     
==========================================
  Files         291      291              
  Lines       65044    65089      +45     
==========================================
+ Hits        51932    51951      +19     
- Misses      12557    12583      +26     
  Partials      555      555              

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