Handle formula extraction from TML models

[mars-lan]

🤔 Why?

ThoughtSpot recently introduced models in favor or Worksheets. This has caused the crawler to crash when extracting formula from models:

Traceback (most recent call last):
  File "/usr/local/lib/python3.9/site-packages/metaphor/common/runner.py", line 61, in run_connector
    entities = connector.run_async()
  File "/usr/local/lib/python3.9/site-packages/metaphor/common/base_extractor.py", line 39, in run_async
    return asyncio.run(self.extract())
  File "/usr/local/lib/python3.9/asyncio/runners.py", line 44, in run
    return loop.run_until_complete(main)
  File "/usr/local/lib/python3.9/asyncio/base_events.py", line 647, in run_until_complete
    return future.result()
  File "/usr/local/lib/python3.9/site-packages/metaphor/thought_spot/extractor.py", line 105, in extract
    self.fetch_virtual_views()
  File "/usr/local/lib/python3.9/site-packages/metaphor/thought_spot/extractor.py", line 137, in fetch_virtual_views
    self.populate_formula()
  File "/usr/local/lib/python3.9/site-packages/metaphor/thought_spot/extractor.py", line 298, in populate_formula
    if column.name in column_expr_map:

🤓 What?

• Add formula extraction support for models returned from the TML export API.
• Gracefully handle all unknown TML object types.

🧪 Tested?

Verified against a production instance.

☑️ Checks

• My PR contains actual code changes, and I have updated the version number in pyproject.toml.

[github-actions]

☂️ Python Coverage

current status: ✅

Overall Coverage

Lines	Covered	Coverage	Threshold	Status
13634	12201	89%	85%	🟢

New Files

No new covered files...

Modified Files

File	Coverage	Status
metaphor/thought_spot/extractor.py	90%	🟢
metaphor/thought_spot/models.py	98%	🟢
TOTAL	94%	🟢

updated for commit: a91caff by action🐍

[codecov]

Codecov Report

Attention: Patch coverage is 37.50000% with 5 lines in your changes missing coverage. Please review.

Project coverage is 89.48%. Comparing base (14eef78) to head (a91caff).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
metaphor/thought_spot/extractor.py	0.00%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1069      +/-   ##
==========================================
- Coverage   89.51%   89.48%   -0.03%     
==========================================
  Files         210      210              
  Lines       13627    13634       +7     
==========================================
+ Hits        12198    12201       +3     
- Misses       1429     1433       +4     

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[alyiwang]

LGTM