Agent Get Pending Message

[Future-Outlier]

Description.

Two months ago, I introduced the Databricks agent service.
Currently, job statuses progress from "pending" to "running" to "succeeded".
To enhance user experience, @pingsutw, @kumare3, and I propose enriching the "pending" status with additional information for Databricks API and future implementations.
This update will relay detailed messages to the Flyte console to keep users informed.

Checks

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

Screenshots

Follow-up issue

#4115
flyteorg/flytekit#1834
#3936

[codecov]

Codecov Report

All modified lines are covered by tests ✅

Comparison is base (4ee73f5) 59.44% compared to head (8e319a2) 59.90%.
Report is 1 commits behind head on master.

❗ Current head 8e319a2 differs from pull request most recent head 16dac19. Consider uploading reports for the commit 16dac19 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4106      +/-   ##
==========================================
+ Coverage   59.44%   59.90%   +0.46%     
==========================================
  Files         637      568      -69     
  Lines       54262    40945   -13317     
==========================================
- Hits        32254    24527    -7727     
+ Misses      19467    14041    -5426     
+ Partials     2541     2377     -164     

Flag	Coverage Δ
unittests	?

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Files	Coverage Δ
...lyteplugins/go/tasks/pluginmachinery/core/phase.go	21.50% <ø> (-1.27%)	⬇️
...yteplugins/go/tasks/plugins/webapi/agent/plugin.go	71.82% <100.00%> (+5.92%)	⬆️

... and 572 files with indirect coverage changes

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