feat: Deephaven UI table databar support

[mattrunyon]

Changes needed for dh.ui databars

• Support for extracting data in viewport columns not listed in table.columns. This allows us to hide the aggregation columns for databars from the user but still get their data. If a column is not in table.columns then it will be added to viewport data via its name instead of model index
• Improved gradient rendering to be much more efficient
• Fixed opacity being ignored if a gradient was used
• Fixed some of the databar spacing (was 1px off center)
• Modified colorValueStyle to have overrides so if we pass a string we don't get back string | undefined when we know we'll get a string
• Modified resolveCssVariablesInRecord to always resolve CSS colors regardless of if they contain a variable

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 18.91892% with 60 lines in your changes missing coverage. Please review.

Project coverage is 46.64%. Comparing base (5b4ce50) to head (850d476).

Files	Patch %	Lines
packages/grid/src/DataBarCellRenderer.ts	3.44%	56 Missing :warning:
...ckages/iris-grid/src/IrisGridTableModelTemplate.ts	57.14%	3 Missing :warning:
packages/iris-grid/src/IrisGridTreeTableModel.ts	0.00%	1 Missing :warning:

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2190   +/-   ##
=======================================
  Coverage   46.64%   46.64%           
=======================================
  Files         692      692           
  Lines       38578    38571    -7     
  Branches     9758     9855   +97     
=======================================
- Hits        17995    17992    -3     
+ Misses      20530    20526    -4     
  Partials       53       53           

Flag	Coverage Δ
unit	46.64% <18.91%> (+<0.01%)	:arrow_up:

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