Conditional formatting: option to apply color to cell text instead of (or in addition to) cell background

**What problem will this feature request solve?**
- Currently, conditional formatting in table and pivot table visualizations only applies color to the cell background.
- There is no option to color just the text/value in a cell.
- This is limiting for users who want to visually flag certain values (e.g. display a number in red) without changing the background color of the entire cell, which can feel visually heavy or clash with dashboard styling.

**Describe the solution you'd like.**
Add an option in the conditional formatting rule settings to choose whether the color is applied to the cell background (current behavior) or the cell text/value. If a user wants to apply formatting to both, they should be able to configure two separate colors — one for the cell background and one for the text — so that the two remain distinguishable and the text doesn't disappear into the background.

**Additional information**
A related issue exists for Number and Detail card visualizations ([#63709](https://github.com/metabase/metabase/issues/63709)), which mentions text color as part of the ask for those viz types — this issue is specifically focused on table and pivot table conditional formatting.

Start by tracing the conditional formatting rule settings and rendering paths for table and pivot table visualizations. Confirm how existing background colors are configured, then define done as allowing separate background and text/value colors, including both together while keeping the text readable.

Written by the indexing model from the issue text.