fix: ensure export() always captures full table

[machow]

This PR refactors the GT.save() function to be a bit more robust, by...

• Screenshotting table element directly (prev screenshotted full window, then cropped using PIL)
• Dumping images into _browser-tests.html in our CI, and uploading as an artifact
• Supporting two debugging modes
  • opening a debugging port (accessible via e.g. chrome://inspect)
  • optionally dumping full browser screenshots with elements highlighted w/ borders (supports dumping at 3 stages: zoom, width_resize, final_resize).

This PR supercedes (aka cribs) the best parts of...

• 276

• 300

This PR should resolve...

• https://github.com/posit-dev/great-tables/issues/234

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 61.66667% with 23 lines in your changes are missing coverage. Please review.

Project coverage is 83.10%. Comparing base (7eae1f2) to head (28f8cf8).

Files	Patch %	Lines
great_tables/_export.py	61.01%	23 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #344 +/- ## ========================================== - Coverage 83.51% 83.10% -0.42% ========================================== Files 41 41 Lines 4308 4338 +30 ========================================== + Hits 3598 3605 +7 - Misses 710 733 +23 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.

[machow]

Woof--I think it's working! See exported table save artifact here!

https://github.com/posit-dev/great-tables/actions/runs/9102189412/artifacts/1506782484

[rich-iannone]

This is incredibly awesome! My only suggestion: take Pillow out of pyproject.toml.

[machow]

It's tucked away in extra installs, so hopefully shouldn't be too bad?! I'm going to merge, but can open a new PR for that if useful!