Fix #6372 Makes WebTorrent extension non-persistent

[AndriusA]

Fix brave/brave-browser#6372

Turning extension background to persistent: false allows browser to unload it when not in use. To avoid launching the extension on every page activity/tab switch/window switch needed to switch to using webNavigation events that can be filtered by URL patterns.

Completely removed window event handling as no key functionality appears to depend on it.

Removed most of tab events, only leaving chrome.tabs.onRemoved to keep torrent cleanup for now.

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:

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.

[cezaraugusto]

Code LGTM. No errors logged in the extension while doing a manual test.

Manual tests included downloading a .torrent file and clicking a magnet link. Both worked as expected in both possible scenarios (webtorrent on/off).

[petemill]

I would suggest this needs an issue with QA/yes where the test plan looks at the task manager for the webtorrent extension process to only show up when in use, and then quit itself again afterwards.

[yrliou]

LGTM, also tested on local and it worked as expected.

[yrliou]

CI is green already, labeled CI/skip for the incoming console log removal.