Implement cosmetic blocking [tracking]

Notes for QA (edit by @bsclifton)

• In 1.5, Cosmetic filtering needs to be enabled via brave://flags/#brave-adblock-cosmetic-filtering
• It wasn’t until 1.6 that this setting’s default value was changed from false to true (see this PR for more info)
• https://github.com/brave/brave-core/pull/3303 (original implementation) only mentions automated tests, does not feature a test plan

Test Plan

In 1.5: First, enable cosmetic filtering via brave://flags/#brave-adblock-cosmetic-filtering

Then, in both 1.5 and 1.6: Navigate to https://enpt.dict.cc in a new tab Ensure there is no large square whitespace under the word “Advertisement” in the center of the page (by the “dict.cc Dicionário Inglês-Português: Portuguese-English and Multilingual Dictionary” header)

Description

Would be great to support EasyList and similar cosmetic filter rules. Much of this work has already been done in https://github.com/brave/adblock-rust. This issue is a tracking issue to keep track of all the branches and changes needed across multiple projects to land this in brave-browser.

[antonok-edm]

@szaimen crashes on Windows should be fixed as of https://github.com/brave/brave-core/pull/4540.

Currently there are no additional settings regarding cosmetic filtering; this work supports the cosmetic filters that will soon be shipped from our filter lists.

The feature flag will be on by default with https://github.com/brave/brave-core/pull/4511.

[bsclifton]

When another fix is attempted, we’ll want to link to test plan if manual QA is required. If not and everything is covered by automation, we can change label to QA/No