fix(dired): prevent dirvish redisplay feedback loop in multi-frame setups

[kovan]

Summary

• When dirvish is open in two frames simultaneously, the preview panes flicker rapidly
• Root cause: dirvish-pre-redisplay-h (on pre-redisplay-functions) fires for every window needing redisplay, but unconditionally calls dirvish--redisplay. When two frames each have dirvish, this creates a feedback loop: frame A's redisplay triggers frame B's and vice versa
• Fix: add :around advice that only calls the original function when the window being redisplayed is the selected window in its frame, breaking the cross-frame loop

Ref: alexluigit/dirvish#353
Fix: #8355

Test plan

• Open a dirvish buffer in one frame
• Create a second frame (make-frame) and open dirvish there too
• Verify neither frame flickers
• Navigate files in both frames — preview should work normally

---

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[kovan]

Upstream PR submitted: alexluigit/dirvish#371

[hlissner]

LGTM! Thanks again, and for PRing this upstream!