feat(cooldown-manager): add text color customization for tracking bars

[Soothx]

What does this PR do?

This PR adds the ability to customize the text colors of Name, Duration and Stacks on Tracking Bars. Previously, the text was always #FFFFFF with 0.9 opacity. This lets the user pick any color. Personally, I made this because the slightly lower opacity white text, next to other completely white text, looked off slightly off.

How was it tested?

I've tested by using various colors. This is only static colors, so it's only applied during ApplyTrackedBuffBarSettings, where it persists. Color also applies correctly in the preview, and persists during reloads.

Also tested on PTR target dummies.
Note: I do not seem to be able to get the "decimals" toggle to work on PTR, with or without the changes here. GetBuildInfo() reports version 120100.

Screenshots

Before:

After:

Wow_n8cAW7Ghsa.mp4

Wow_89Otv6nVBU.mp4

Checklist

• New settings default OFF (no behavior change without opt-in)
• Zero cost while disabled: no events registered, no polling, no hooks doing work, no frames built
• Cheap while enabled: event-driven (no polling, no timer-based logic, no per-frame allocations)
• No writes onto Blizzard-owned frames (weak-table pattern used); HookScript/hooksecurefunc only, never SetScript on Blizzard frames
• Tested in-game, works on live retail; no load errors on the 12.1 PTR client