fix(overlay): fix to support filtor-dialog of efx-grid

[Theeraphat-Sorasetsakul]

Description

Can't click at EFX grid filter dialog when grid is in EF dialog

To reproduce and solution: You can try at test/overlay-filter-dialog branch.

1. Set zIndex property to override zIndex default behaviour of ef-overlay.
2. Set CSS zindex=0 to ef-dialog to prevent auto zindex calculation.
3. Set CSS zindex=0 or above and set pointer-event=auto to filter-dialog.

Fixes # (issue)

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I have checked my code and corrected any misspellings

[cloudflare-workers-and-pages]

Deploying refinitiv-ui with    Cloudflare Pages

Latest commit:	bded1c5
Status:	✅  Deploy successful!
Preview URL:	https://7e5878a0.refinitiv-ui.pages.dev
Branch Preview URL:	https://v6-fit-overlay-add-zindex-ty.refinitiv-ui.pages.dev

View logs