Update UI styles for query assist

[joshuali925]

Description

• styling change to query assist
  • move NLQ input above query textarea
  • wrap component in collapsible accordion
  • merge Generate query and Generate and run into a split button
  • update wording
• guardrail support: display error callout if guardrail is triggered

Issues Resolved

[List any issues this PR will resolve]

Check List

• New functionality includes testing.
  • All tests pass, including unit test, integration test and doctest
• New functionality has been documented.
  • New functionality has javadoc added
  • New functionality has user manual doc added
• Commits are signed per the DCO using --signoff

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[codecov]

Codecov Report

Attention: Patch coverage is 54.54545% with 40 lines in your changes are missing coverage. Please review.

Project coverage is 56.97%. Comparing base (d17cad3) to head (dcb9247).
Report is 2 commits behind head on main.

Files	Patch %	Lines
...ts/event_analytics/explorer/query_assist/input.tsx	56.06%	27 Missing and 2 partials ⚠️
public/components/common/search/query_area.tsx	0.00%	8 Missing ⚠️
...components/event_analytics/explorer/no_results.tsx	40.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1523      +/-   ##
==========================================
+ Coverage   56.62%   56.97%   +0.34%     
==========================================
  Files         348      348              
  Lines       12656    12748      +92     
  Branches     3202     3294      +92     
==========================================
+ Hits         7167     7263      +96     
+ Misses       5436     5429       -7     
- Partials       53       56       +3     

Flag	Coverage Δ
dashboards-observability	56.97% <54.54%> (+0.34%)	⬆️

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