Remove deprecated InjectDecoder

[EngHabu]

Tracking issue

#4508

Describe your changes

Controller Runtime deprecated (and completely removed) the dependency injection framework it used to have (review breaking changes section here: https://github.com/kubernetes-sigs/controller-runtime/releases/tag/v0.15.0). Unfortunately this breaks very silently. InjectDecoder() is the only place as far as I can tell where we rely on that functionality. When decoders are not injected, the secrets webhook fails to parse out Pods to inject secrets too.

Check all the applicable boxes

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

Screenshots

Before:

After:

Note to reviewers

Related PRs

PR that upgraded Controller Runtime to the breaking version: https://github.com/flyteorg/flyte/pull/4273/files

[codecov]

Codecov Report

Attention: 10 lines in your changes are missing coverage. Please review.

Comparison is base (7481b3d) 59.39% compared to head (50b6d4d) 59.40%.

Files	Patch %	Lines
flytepropeller/pkg/controller/controller.go	0.00%	6 Missing ⚠️
flytepropeller/pkg/webhook/entrypoint.go	0.00%	3 Missing ⚠️
flytepropeller/pkg/webhook/pod.go	80.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4507      +/-   ##
==========================================
+ Coverage   59.39%   59.40%   +0.01%     
==========================================
  Files         638      638              
  Lines       53959    53954       -5     
==========================================
+ Hits        32048    32051       +3     
+ Misses      19382    19374       -8     
  Partials     2529     2529              

Flag	Coverage Δ
unittests	59.40% <28.57%> (+0.01%)	⬆️

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