Cleanup ContentBlockerManager and improve its speed.

[cuba]

Description:

The content blocker manager uses a timed sync mechanism. Because apple caches rule lists, this is actually not needed. We don't need to recompile anything on re-launches, just when settings and data changes.

This caching way makes it very difficult to work with custom filter lists and adds extra overhead on background threads for no reason.

Additional Information

[Uni-verse]

Verified on iPhone X running iOS 16.3.1 using version 1.50 (23.4.25.20)

Using Test Plan in #7131 (comment)

• Ensured that page has true for all values when loading https://test-pages.privacytests.org/tracking_content.html.
• Ensured that app launches relatively quickly with many filters enabled in the content filtering.
• Ensured that cosmetic filtering is working when loading twitter.com or reddit.com
• Ensured that script loading test page is passing, showing true when shields are up and null when shields down - https://dev-pages.brave.software/filtering/scriptlets.html

Example	Example	Example	Example	Example	Example