Add separate worker for scam, so it can handle RC updates immediately

[CrisBarreiro]

Task/Issue URL: https://app.asana.com/0/0/1209893469792815/f

Description

Steps to test this PR

Feature 1

• Fresh install the app
• Using the app inspector, check that only phishing and malware datasets are present. Data needs to be downloaded, so it might take a few seconds to complete. The easiest way is to check the revisions table in malicious_sites db
• Open https://privacy-test-pages.site/security/badware/phishing.html and check it's blocked
• Open https://privacy-test-pages.site/security/badware/malware.html and check it's blocked
• Open https://privacy-test-pages.site/security/badware/scam.html and check it's not blocked

Feature 2

• Without reinstalling the app, enable scamProtection under Feature Flag Inventory and restart the app
• Using the app inspector, check that phishing, malware and scam datasets are present. Data needs to be downloaded, so it might take a few seconds to complete. The easiest way is to check the revisions table in malicious_sites db
• Open https://privacy-test-pages.site/security/badware/scam.html and check it's blocked.
• Disable scamProtection under Feature Flag Inventory and restart the app
• Open https://privacy-test-pages.site/security/badware/scam.html and check it's not blocked

UI changes

Before	After
!(Upload before screenshot)	(Upload after screenshot)

[CrisBarreiro]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• Enable scam protection for internal users #5875
• Add separate worker for scam, so it can handle RC updates immediately #5857 👈 (View in Graphite)
• Add support for scam protection #5853
• develop

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