Implement defined queries

[ahuang11]

This PR implements two new features with predefined SQL queries:

1. A defined_queries parameter for storing predefined SQL queries that users can trigger individually or all together with a click of a button
2. A QueryLookup tool that embeds these queries and suggests relevant ones based on user questions

These defined queries are defined in the Coordinator class which are displayed as clickable buttons under suggestions

The QueryLookup class extends VectorLookupTool for embedding of SQL queries and their descriptions. Not sure if I should just use DocumentLookup...?

If defined queries exist, the SQLAgent could use QueryLookup, but also still debating whether it's a Coordinator/Planner or SQLAgent thing.

Also implements a fast track method to immediately call QueryLookup -> SQLAgent -> VegaLiteAgent

[codecov]

Codecov Report

Attention: Patch coverage is 8.60927% with 138 lines in your changes missing coverage. Please review.

Project coverage is 54.83%. Comparing base (4986773) to head (5d91065).

Files with missing lines	Patch %	Lines
lumen/ai/coordinator.py	3.84%	100 Missing ⚠️
lumen/ai/tools.py	17.39%	38 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##            gated    #1144      +/-   ##
==========================================
- Coverage   55.26%   54.83%   -0.44%     
==========================================
  Files         112      112              
  Lines       15993    16143     +150     
==========================================
+ Hits         8839     8852      +13     
- Misses       7154     7291     +137     

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