Filter user-tracking parameters from query string

[fmarier]

Fixes brave/brave-browser#4239.

If a URL's query string includes one of the parameter names known
to track individual users, we remove them.

https://support.google.com/analytics/answer/7519794
https://stackoverflow.com/questions/52847475/what-is-fbclid-the-new-facebook-parameter
https://about.ads.microsoft.com/en-us/blog/post/january-2018/conversion-tracking-update-on-bing-ads
https://developer.mailchimp.com/documentation/mailchimp/guides/getting-started-with-ecommerce/#e-commerce-tracking-and-reports

Submitter Checklist:

• Submitted a ticket for my issue if one did not already exist.
• Used Github auto-closing keywords in the commit message.
• Added/updated tests for this change (for new code or code which already has tests).
• Verified that these changes build without errors on
  • Android
  • iOS
  • Linux
  • macOS
  • Windows
• Verified that these changes pass automated tests (unit, browser, security tests) on
  • iOS
  • Linux
  • macOS
  • Windows
• Verified that all lint errors/warnings are resolved (npm run lint)
• Ran git rebase master (if needed).
• Ran git rebase -i to squash commits (if needed).
• Tagged reviewers and labelled the pull request as needed.
• Request a security/privacy review as needed.
• Add appropriate QA labels (QA/Yes or QA/No) to include the closed issue in milestone
• Public documentation has been updated as necessary. For instance:
  • https://github.com/brave/brave-browser/wiki/Deviations-from-Chromium-(features-we-disable-or-remove)
  • https://github.com/brave/brave-browser/wiki/Proxy-redirected-URLs
  • https://github.com/brave/brave-browser/wiki/Fingerprinting-Protection-Mode
  • https://github.com/brave/brave-browser/wiki/Brave%E2%80%99s-Use-of-Referral-Codes
  • https://github.com/brave/brave-browser/wiki/Custom-Headers
  • https://github.com/brave/brave-browser/wiki/Web-compatibility-issues-with-tracking-protection
  • https://github.com/brave/brave-browser/wiki/QA-Guide

Test Plan:

Visit the following URLs:

• https://brave.com/?fbclid=1234
• https://brave.com/?gclid=1234
• https://brave.com/?msclkid=1234
• https://brave.com/?mc_eid=1234

and verify that the query string is removed and that the URL bar only shows https://brave.com/.

Reviewer Checklist:

• New files have MPL-2.0 license header.
• Request a security/privacy review as needed.
• Adequate test coverage exists to prevent regressions
• Verify test plan is specified in PR before merging to source

After-merge Checklist:

• The associated issue milestone is set to the smallest version that the
  changes has landed on.
• All relevant documentation has been updated.

[fmarier]

Note to reviewers: while the custom query string parsing code is unfortunate, Chromium's url::ExtractQueryKeyValue() (which actually comes from Mozilla) makes a lot of assumptions about how the query string is supposed to be structured and cannot distinguish between these:

• ?foo
• ?foo=
• ?foo&

Given that the format of the query string is not specified in RFC 3986, some frameworks don't agree with the way that the Mozilla parser interprets the query string and instead considers ?foo an empty key with a value of foo.

My parser aims at keeping to a minimum the changes we make to the query string and handles seemingly invalid query strings just fine. I have tried to optimize for the cases where (1) there is no query string and (2) the query string doesn't include any of the trackers.

[iefremov]

Besides minors and nits, I think we should try to simplify the parsing part.

[fmarier]

After a discussion on Slack with @iefremov and @bridiver , we came to the conclusion that we should replace the string manipulation code with regular expressions:

s/&(fbclid|gclid|msclkid|mc_eid)=[^&]+//g
s/^(fbclid|gclid|msclkid|mc_eid)=[^&]+&//g
s/^(fbclid|gclid|msclkid|mc_eid)=[^&]+$//g

All review comments addressed in latest revision.