Enhance Find Mode Performance and Responsiveness

[darpham]

Problem Statement:

When using find mode (/) on large web pages, searching is slow to the point of unusable.
Reproducible via https://nix-community.github.io/home-manager/options.xhtml.

Planned Improvements:

• Delay / debounce FindMode.findInPlace() to reduce the frequency of searches during typing.
  • InReview Add debounce to HUD.search() method #4547
• Implement a caching mechanism for text nodes, potentially using SimpleCache from ./lib/utils.js.
• Offload text searching to a Web Worker or run asynchronously, possibly utilizing AsyncDataFetcher from ./lib/utils.js.

Expected Benefits:

• Improved responsiveness during rapid typing in find mode.
• Faster search performance, especially on large web pages.
• Reduced strain on system resources during find operations.

[UncleSnail]

The first task should be sufficient. The second two are good ideas, but are probably unneeded and would introduce unnecessary complexity.
I like the idea for the debounce though, and this is a real issue. It also freezes on your example page on my machine. I'm going to take a look at your PR.