fix(common): handle dynamic scroll ancestors and cell CSS overlays

[ghiscoding]

replicate Slickgrid-Universal PR 2735 into SlickGrid. You can see the included ChatGPT summary below.

asked Codex to review very old TODOs left in SlickGrid file by the original author and fixed using ChatGPT Terra 5.6 model

Summary

• Replace static ancestor scroll bindings with a capture-phase listener that continues working when the grid is reparented.
• Merge keyed cell CSS overlays when styles are added, updated, or removed, avoiding repeated lookups during cell rendering.
• Add unit tests covering both behaviors.

Validation

• SlickGrid core and RTL tests: 443 passed
• TypeScript check with tsc --noEmit
• Prettier and Oxlint checks passed

column-rendering loop TODOs remain deferred for separate work.