Vertex AI Model Handler Private Endpoint Support

[jrmccluskey]

Tightens retry logic to service-side errors and explicit 429s, explicitly handles private Vertex AI endpoints to support request sizes above 1.5 MB, adds some sanity-checking for args to the model handler (largely private + network pairing,) and makes the example pipeline compatible with private endpoints.

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[Codecov]

Codecov Report

Merging #27696 (01a5389) into master (d822fc9) will increase coverage by 0.00%.
Report is 49 commits behind head on master.
The diff coverage is 35.29%.

@@           Coverage Diff           @@
##           master   #27696   +/-   ##
=======================================
  Coverage   70.93%   70.94%           
=======================================
  Files         861      861           
  Lines      104807   104821   +14     
=======================================
+ Hits        74344    74363   +19     
+ Misses      28905    28900    -5     
  Partials     1558     1558           

Flag	Coverage Δ
python	80.02% <35.29%> (+0.01%)	⬆️

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Files Changed	Coverage Δ
...amples/inference/vertex_ai_image_classification.py	0.00% <0.00%> (ø)
...on/apache_beam/ml/inference/vertex_ai_inference.py	44.77% <40.00%> (+1.91%)	⬆️

... and 12 files with indirect coverage changes

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[jrmccluskey]

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[jrmccluskey]

R: @damccorm

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Stopping reviewer notifications for this pull request: review requested by someone other than the bot, ceding control

[damccorm]

LGTM!