several shields panel improvements

[cezaraugusto]

Submitter Checklist:

fix brave/brave-browser#1894
fix brave/brave-browser#1892
fix brave/brave-browser#2488
fix brave/brave-browser#2565

Test Plan:

1. Ensure all features on shields work

• Ads/Trackers should bump in sites such as https://wired.com
• HTTPSE should respond to https://https-everywhere.badssl.com
• Cookies should respond to http://www.html-kit.com/tools/cookietester/
• Fingerprinting should respond to https://codepen.io/run-time/pen/XJNXWV

2. Ensure shields is accessible via keyboard using tab for navigation, space for actions. enter should work for buttons as well.

3. Ensure the general (not scripts) blocked list (accessed via arrow down icon) can be scrolled both horizontally and vertically

4. Issue Click on All scripts allowed shield setting, displays blank drop down for few seconds before loading drop down options brave-browser#2488 is being set as fixed as scripts now use a toggle instead of a select element

5. Shields should look like the original spec available here

6. Ensure that once a given resource stat reach 0, the option to show resources blocked should have no interactions other than toggling switch on/off

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

[bsclifton]

@cezaraugusto does 3rd party device recognition blocking work? (should it be included?)

[bsclifton]

When going into a details screen (ex: in the above screenshot, you can expand 2 to see the list of 3rd-party trackers blocked), there isn't really an immediate keyboard shortcut (that I found) for going "back" to the general shields screen.

• If you hit escape, it closes the shields menu completely
• pushing enter didn't engage the button for me
• if you manually choose the Go Back button and hit space, it works as expected
• also if you hit tab at least once and then hit enter

[cezaraugusto]

@bsclifton re third-party scripts this is something I'm investigating but it has the same behavior in current release so if that's a bug it isn't new.

re keyboard shortcut there's no immediate closing but you can do it via space bar in the arrow's row or by space/enter in the bottom button. esc closes the extension but I think this is the default behavior

[bsclifton]

Comments I had addressed by @cezaraugusto in follow up comment

I went through test plan, worked great; keyboard worked especially great. This is a SUPER nice upgrade 😄 Well done! 🥇

[cezaraugusto]

re fingerprinting I created brave/brave-browser#3698 to keep track.

since test plan works, PR is reviewed and both product and design agree with changes applied here I'm going to hit merge. if for some reason other reviewers still have feedback to give please comment and I can come with a follow-up. thanks all!