Add support for sharing models across steps

[damccorm]

Sometimes it is useful to have 2 steps that use the same model (e.g. an LLM doing 2 different tasks at different parts of the pipeline). This enables that behavior via a flag passed to the RunInference instance

---

Thank you for your contribution! Follow this checklist to help us incorporate your contribution quickly and easily:

• Mention the appropriate issue in your description (for example: addresses #123), if applicable. This will automatically add a link to the pull request in the issue. If you would like the issue to automatically close on merging the pull request, comment fixes #<ISSUE NUMBER> instead.
• Update CHANGES.md with noteworthy changes.
• If this contribution is large, please file an Apache Individual Contributor License Agreement.

See the Contributor Guide for more tips on how to make review process smoother.

To check the build health, please visit https://github.com/apache/beam/blob/master/.test-infra/BUILD_STATUS.md

GitHub Actions Tests Status (on master branch)

See CI.md for more information about GitHub Actions CI or the workflows README to see a list of phrases to trigger workflows.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 71.41%. Comparing base (aabf7d0) to head (db22dc4).
Report is 16 commits behind head on master.

❗ Current head db22dc4 differs from pull request most recent head 83e7b79

Please upload reports for the commit 83e7b79 to get more accurate results.

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #31665      +/-   ##
============================================
+ Coverage     71.40%   71.41%   +0.01%     
  Complexity     1474     1474              
============================================
  Files           900      900              
  Lines        114179   114219      +40     
  Branches       1076     1076              
============================================
+ Hits          81526    81573      +47     
+ Misses        30624    30617       -7     
  Partials       2029     2029              

Flag	Coverage Δ
python	81.29% <100.00%> (+0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[damccorm]

R: @jrmccluskey

[github-actions]

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

[jrmccluskey]

LGTM! Super simple to add, very cool feature

[rezarokni]

For future PR, would be interesting to explore if there is a way to determine if a user has accidentally set the same tag for different models.