Fix: avoid log spam for log links generated during the pod's pending phase

[fg91]

Why are the changes needed?

In #4726 I introduced the option to configure the lifecycle of log links as is documented here. In particular, log links can be configured to be already shown before a task starts running or be configured to disappear after a task stops.

@Tom-Newton noted that their flytepropeller logs are spammed with error messages because the log link generation logic for pod tasks checks whether container statuses exist and if not logs this as an error. Prior to #4726 it made sense to always log this as an error because log links were only generated in the "Running" phase of the task when the pod should have container statuses. Now that we optionally generate log links already in the pending phase, it is not unexpected that the container statuses are empty.

What changes were proposed in this pull request?

Log the respective message with debug log level if the pod is in the pending phase. Keep logging with error log level in other pod phases.

Check all the applicable boxes

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

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 8 lines in your changes missing coverage. Please review.

Project coverage is 36.84%. Comparing base (2b0af2b) to head (6d125d8).
Report is 143 commits behind head on master.

Files with missing lines	Patch %	Lines
flyteplugins/go/tasks/logs/logging_utils.go	0.00%	8 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5945      +/-   ##
==========================================
- Coverage   36.84%   36.84%   -0.01%     
==========================================
  Files        1309     1309              
  Lines      130994   131001       +7     
==========================================
- Hits        48271    48269       -2     
- Misses      78533    78543      +10     
+ Partials     4190     4189       -1     

Flag	Coverage Δ
unittests-datacatalog	51.58% <ø> (ø)
unittests-flyteadmin	54.10% <ø> (ø)
unittests-flytecopilot	11.73% <ø> (ø)
unittests-flytectl	62.40% <ø> (-0.05%)	⬇️
unittests-flyteidl	6.92% <ø> (ø)
unittests-flyteplugins	53.62% <0.00%> (-0.02%)	⬇️
unittests-flytepropeller	43.02% <ø> (ø)
unittests-flytestdlib	55.41% <ø> (+0.01%)	⬆️

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[Tom-Newton]

Thanks