Add Agent Get Message Proto

[Future-Outlier]

TL;DR

As title.

Type

• Bug Fix
• Feature
• Plugin

Are all requirements met?

• Code completed
• Smoke tested
• Unit tests added
• Code documentation added
• Any pending items have an associated Issue

Complete description

Enable agent to get state message.
For example, agent can return the state message when using the databricks service.

Follow-up issue

flyteorg/flyteplugins#399
flyteorg/flytekit#1834

[codecov]

Codecov Report

Patch coverage has no change and project coverage change: +2.55% 🎉

Comparison is base (7f62a15) 75.92% compared to head (5c84ed9) 78.48%.

❗ Current head 5c84ed9 differs from pull request most recent head e92256c. Consider uploading reports for the commit e92256c to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #440      +/-   ##
==========================================
+ Coverage   75.92%   78.48%   +2.55%     
==========================================
  Files          18       18              
  Lines        1458     1250     -208     
==========================================
- Hits         1107      981     -126     
+ Misses        294      212      -82     
  Partials       57       57              

Flag	Coverage Δ
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see 18 files with indirect coverage changes

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[Future-Outlier]

Please approve it again!
Thanks a lot!