chore: Upgrade Rust to 1.84

[BulkBeing]

Also upgrades some of the dependencies, notably Axum to 0.8.2.
Removes rust/Dockerfile. We do not use this file.

Verified by running Monovertex test/monovertex-e2e/testdata/mono-vertex-with-transformer.yaml

[codecov]

Codecov Report

Attention: Patch coverage is 66.66667% with 2 lines in your changes missing coverage. Please review.

Project coverage is 68.04%. Comparing base (c492520) to head (473b4cc).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
rust/numaflow-core/src/lib.rs	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2349      +/-   ##
==========================================
+ Coverage   67.94%   68.04%   +0.10%     
==========================================
  Files         352      352              
  Lines       46527    46498      -29     
==========================================
+ Hits        31613    31640      +27     
+ Misses      13833    13784      -49     
+ Partials     1081     1074       -7     

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[vigith]

we also need to upgrade tower to 0.5.2, currently it is 0.4.x