Upgrade from Chromium 83 to Chromium 84

[mkarolin]

Upgrade from Chromium 83.0.x.x to Chromium 83.0.4147.XX

https://chromium.googlesource.com/chromium/src/+log/83.0.4103.106..84.0.4147.56/?pretty=fuller&n=10000

QA tests:
This is a major Chromium version bump, please do full passes.

Affected areas:

1. Settings page.
   • Please thoroughly test all our settings modifications, e.g. "clear data on exit", content settings categories (if we still customize those), brave theme, shields preferences, and strings, etc.
2. All Chromium WebUI's (settings, history, downloads, bookmarks, extensions):
   • Are buttons, toggles, links, checkboxes all using brave colors (red and not blue)?
   • Does the toolbar and the toolbar search work properly?
3. Importing encrypted data from Brave/Chrome/Chromium on Linux.
4. Crash reporting (verify that reports arrive to our server).
5. Settings UI: check that Brave version shows correctly.
6. Check that Shields settings are preserved on browser exist/restart.
7. Check ability to download/update extensions.

[kjozwiak]

Labeling following as QA/No in favour of #10594. We'll also mention that the area's that @mkarolin mentioned via #10364 (comment) get tested in #10594.