Use `CookieStore` API instead of accessing `document.cookie` if supported

[piquark6046]

Prerequisites

• I verified that this is not a filter list issue. Report any issues with filter lists or broken website functionality in the uAssets issue tracker.
• This is NOT a YouTube, Facebook or Twitch report. These sites MUST be reported by clicking their respective links.
• This is not a support issue or a question. For support, questions, or help, visit /r/uBlockOrigin.
• I performed a cursory search of the issue tracker to avoid opening a duplicate issue.
• The issue is not present after disabling uBO in the browser.
• I checked the documentation to understand that the issue I am reporting is not normal behavior.

I tried to reproduce the issue when...

• uBO is the only extension.
• uBO uses default lists and settings.
• using a new, unmodified browser profile.

Description

https://developer.mozilla.org/en-US/docs/Web/API/CookieStore
AdguardTeam/Scriptlets#521

A specific URL where the issue occurs.

Any webpage that `set-cookie` or `trusted-set-cookie` scriptlet filter applies.

Steps to Reproduce

1. Visit the webpage.

Expected behavior

Use CookieStore API to modify the cookie.

Actual behavior

Use document.cookie.

uBO version

latest

Browser name and version

Firefox

Operating System and version

Ubuntu

[jvoisin]

What would be the point of doing this?

[u-RraaLL]

Probably not something to be changed anytime soon. We'd need to bump the minimal version for Firefox to 140.

[krystian3w]

Or design with technological debt.