Add support for Adblock Rust library

[srirambv]

Test Plan

See #1441

Follow up to #1307

[kjozwiak]

Verification PASSED on iPhone 6S+ iOS 12.4.1 using the following test cases:

• Upgraded from 1.11.3 (19.08.16.20) --> 1.11.4 (19.08.29.21) and ensured
  • stats under NTP were retained and displayed correctly
  • visiting new websites correctly updated the NTP and updated the stats
  • clicking on the shields panel correctly displayed the correct stats for that particular site
  • ensured that the above cases also worked under PB and NTP/Shields stats were being updated
• Installed 1.11.4 (19.08.29.21) and ensured the same above cases were working as expected
• Installed 1.11.4 (19.08.29.21) and quickly loaded twitter.com, reddit.com, fb.com, buzzfeed.com and ensured NTP/Shield stats were being updated right away

[srirambv]

Verification passed on iPad Pro with iOS 12.4.1 running 1.11.4(19.08.29.21)

• Verified stats are retained during upgrade from 1.11.3 to 1.11.4
• Verified visiting new sites updates stats on NTP
• Verified stats update on visiting sites from Private tab as well
• Verified shields shows correct stats for each site
• Verified removing app from memory and relaunch updates the stats from previous session
• Verified switching between normal and private tabs retain the stats

[srirambv]

Verification passed on iPhone XR with iOS 13.1 PB1 running 1.11.4(19.08.29.21)

• Verified stats are retained during upgrade from 1.11.3 to 1.11.4
• Verified visiting new sites updates stats on NTP
• Verified stats update on visiting sites from Private tab as well
• Verified shields shows correct stats for each site
• Verified removing app from memory and relaunch updates the stats from previous session
• Verified switching between normal and private tabs retain the stats

[LaurenWags]

Verification passed on iPad 5th Gen with iOS 12.3.1 for update to 1.11.4(19.08.29.21)

• Installed 1.11.3 from app store and
  • added bookmarks, history, tabs, stats, cookie, login/password, site specific shield settings, custom sites to Favorites
  • set default search engine to DDG for normal and private tabs
• Updated to 1.11.4(19.08.29.21) using TF.
  • Verified version change 1.11.3 --> 1.11.4
  • Verified stats are retained during upgrade from 1.11.3 to 1.11.4
  • Verified visiting new sites updates stats on NTP
  • Verified stats update on visiting sites from Private tab as well
  • Verified shields shows correct stats for each site
  • Verified removing app from memory and relaunch updates the stats from previous session
  • Verified switching between normal and private tabs retain the stats
  • Verified the following data was retained: bookmarks, history, tabs, cookie, login/password, site specific shield settings, custom sites in Favorites, search engine setting.
  • Verified search engine settings could be changed after upgrade.