feat(cdm): add min-stack threshold gate to bar glows

[erickjmoreno]

What does this PR do?

Adds an opt-in "Require Min Stacks" setting to Cooldown Manager Bar Glows. The glow only starts once the tracked buff/debuff reaches a configured stack/application count (2-99), instead of glowing on presence alone.

Applications counts can be a SECRET value even in open-world content, so the threshold compare never happens in Lua (any compare on a secret value hard-errors). Instead a one-unit StatusBar window [threshold-1, threshold] performs the compare C-side via SetValue, and a mask riding that fill's edge crops the native glow texture -- same technique already used by the per-icon "Glow at Stacks" feature.

How was it tested?

• Verified the new stack cache (ns._tickBlizzAuraStacks) is populated from the same sid/baseSID/linked resolution pass as the existing active cache, so it matches whatever spellID a Bar Glow entry is saved against.
• Verified the option row follows the existing DualRow pattern and is disabled in Buff Missing mode (stacks don't apply there).
• Verified the gate/mask frames are only created lazily on first use (threshold > 1 and glow active), so unopted-in users pay nothing.

Screenshots

N/A -- adds one settings row using the existing DualRow widget shape; no new visual style.

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 on live; no version gates or pre-Midnight APIs added