Implement cosmetic filtering

[pes10k]

Since cosmetic filtering doesn't have the same timing issues as request blocking, it wouldn't need to go through the iOS content blocking / declarative system.

Most (all?) of this information and functionality should already be available in the rust DAT and adblock-rust. Also, likely a lot of the brave-core brave_extension content script code could be reused

[kylehickinson]

Blocked by #3683

[anthonypkeane]

For a spec, please search for "Cosmetic Filters and Scriptlet Injections" in GDrive

[Uni-verse]

Verified using version 1.37 (22.3.29.15)

Devices:
iPhone 12 Pro | iOS 15.4
iPad (7th Gen) | iOS 15.2.1
iPhone X | iOS 14.4.2

• Verified that ads on youtube are blocked correctly.
• Verified that the non-video ads that show up below a video are blocked correctly.

iPhone ads blocked	iPhone in-content ad	iPad ads blocked	iPad in-content ad

[iccub]

Let's reopen to verify together with #5208

[Uni-verse]

Verified using RC #2 version 1.37 (22.4.5.19)

Devices:

• iPhone 12 running iOS 15.4
• iPhone X running iOS 14.4.2
• iPad running iOS 15.2.1

PASS - Verified that ads on youtube are blocked correctly.
PASS - Verified that the non-video ads that show up below a video are blocked correctly.

Shields Off	Shields On

Shields Off (iPad)	Shields On (iPad)