Allow modification of window attributes with scriptlets

[antonok-edm]

Currently, the implementation of scriptlet injection for cosmetic filters is done using the insertScript API, which is sandboxed from the main page. As a result, scriptlets that rely on intercepting method calls on the global window object don't do anything.

uBlock Origin's implementation injects scriptlets by creating a global script HTML element with the scriptlet as the text content, inserting it to the DOM, and immediately removing it after execution. This approach should provide better compatibility.

[srirambv]

Verification passed on

Brave	1.9.62 Chromium: 81.0.4044.138 (Official Build) dev (64-bit)
Revision	8c6c7ba89cc9453625af54f11fd83179e23450fa-refs/branch-heads/4044@{# 999}
OS	Linux

• Verified Paid promotion links are shown on current release build 1.8.95
  
• Verified Paid Promotion links are removed on 1.9.62
  

Verification passed on

Brave | 1.9.62 Chromium: 81.0.4044.138 (Official Build) dev (64-bit)
-- | --
Revision | 8c6c7ba89cc9453625af54f11fd83179e23450fa-refs/branch-heads/4044@{#999}
OS | Windows 10 OS Version 1803 (Build 17134.1006)

• Verified the test plan from Allow modification of window attributes with scriptlets brave-core#5402
• Verified Paid promotion links are shown on current release build 1.8.95
  
• Verified Paid Promotion links are removed on 1.9.62
  

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Verified passed with

Brave | 1.9.62 Chromium: 81.0.4044.138 (Official Build) dev (64-bit)
-- | --
Revision | 8c6c7ba89cc9453625af54f11fd83179e23450fa-refs/branch-heads/4044@{#999}
OS | macOS Version 10.14.6 (Build 18G3020)

• Verified test plan from Allow modification of window attributes with scriptlets brave-core#5402

Using 1.8.95, confirmed I see the Promotional links:

Using 1.9.x, confirmed no Promotional links: