refactor: Remove custom targets, use 'None' item group

[jviau]

Description

This PR refactors the python worker nuget package targets as follows:

1. Removes current custom targets/properties
   1. Properties, items, targets all share the same global namespace. Naming these generally increases risk of conflicts with other props/items/targets.
2. Leverages None item group with appropriate metadata to have CopyToOutputDirectory and CopyToPublishDirectory targets perform the copies for us.
   1. Instead of copying files to output or publish manually, you can add to various existing item groups and tag them to be copied.
   2. This change improves incremental build support, avoiding copies when the files already exist at the destination.
3. Adds additional logic to copy only specific runtime files with a runtime identifier is specified.
   1. Will error out if the runtime identifier is not supported.

One of the main benefits is worker size when deployed for a specific runtime. On linux-x64, the workers/python folder goes from 533MB (all runtimes) to 87.8MB (linux-x64 only copied) (tested with python worker 4.34.0).

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PR information

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• New Unit tests were added for the changes made and CI is passing.

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[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 45.88%. Comparing base (c244569) to head (2f40dbd).
Report is 3 commits behind head on dev.

❗ Current head 2f40dbd differs from pull request most recent head 6586aaf

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Additional details and impacted files

@@             Coverage Diff             @@
##              dev    #1472       +/-   ##
===========================================
- Coverage   83.03%   45.88%   -37.15%     
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  Files          36       35        -1     
  Lines        2322     2040      -282     
  Branches      346      302       -44     
===========================================
- Hits         1928      936      -992     
- Misses        295     1028      +733     
+ Partials       99       76       -23     

Flag	Coverage Δ
unittests	45.88% <ø> (-37.15%)	⬇️

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