Fix: Handle overriding of container image in backend

[fg91]

Tracking issue

flyteorg/flyte#4543

Why are the changes needed?

The container_image task node override, among others, is currently broken (doesn't work with pyflyte register and only once with pyflyte run, see tracking issue.

What changes were proposed in this pull request?

Don't override container image of run_entity in .with_overrides but actually in flyteidl's TaskNodeOverride so that the container image is overridden in the backend.

How was this patch tested?

In combination with flyteorg/flyte#4858 I ensured that the resulting pod in the cluster has the correct image. I also adapted the unit tests.

• I updated the documentation accordingly.
• All new and existing tests passed.
• All commits are signed-off.

Related PRs

flyteorg/flyte#4858

Docs link

[fg91]

Tests are failing because an idl upgrade is needed once flyteorg/flyte#4858 is merged.

[pingsutw]

LGTM, let's merge flyteidl first.

[codecov]

Codecov Report

Attention: Patch coverage is 88.88889% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 84.65%. Comparing base (90324e0) to head (e68a4e8).
Report is 1 commits behind head on master.

Files	Patch %	Lines
flytekit/models/core/workflow.py	85.71%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2176      +/-   ##
==========================================
- Coverage   85.86%   84.65%   -1.21%     
==========================================
  Files         314      314              
  Lines       24042    24048       +6     
  Branches     3643     3644       +1     
==========================================
- Hits        20643    20359     -284     
- Misses       2759     3037     +278     
- Partials      640      652      +12     

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