Hide idle detection UI elements in Settings.

[mkarolin]

Fixes brave/brave-browser#18409

I think I got all the places where it shows up.

Submitter Checklist:

• I confirm that no security/privacy review is needed, or that I have requested one
• There is a ticket for my issue
• Used Github auto-closing keywords in the PR description above
• Wrote a good PR/commit description
• Added appropriate labels (QA/Yes or QA/No; release-notes/include or release-notes/exclude; OS/...) to the associated issue
• Checked the PR locally: npm run test -- brave_browser_tests, npm run test -- brave_unit_tests, npm run lint, npm run gn_check, npm run tslint
• Ran git rebase master (if needed)

Reviewer Checklist:

• A security review is not needed, or a link to one is included in the PR description
• New files have MPL-2.0 license header
• Adequate test coverage exists to prevent regressions
• Major classes, functions and non-trivial code blocks are well-commented
• Changes in component dependencies are properly reflected in gn
• Code follows the style guide
• Test plan is specified in PR before merging

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, 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-Protections
  • 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-Exceptions-in-Brave
  • https://github.com/brave/brave-browser/wiki/QA-Guide
  • https://github.com/brave/brave-browser/wiki/P3A

Test Plan:

[jumde]

lgtm

[stephendonner]

Verified PASSED using

Brave	1.32.34 Chromium: 94.0.4606.61 (Official Build) nightly (x86_64)
Revision	418b78f5838ed0b1c69bb4e51ea0252171854915-refs/branch-heads/4606@{#1204}
OS	macOS Version 11.6 (Build 20G165)

Steps:

1. Start Brave and navigate to any site (e.g. cnn.com)
2. Navigate to brave://settings → "Privacy and security" → "Site and Shields Settings"
3. Under "Permissions" section, click on "Additional permissions"
4. Verify that "Your device use" item is not present
5. Scroll back to the top of the page and click on "View permissions and data stored across sites"
6. Pick the site you visited in step 1 and click to expand
7. Click on the site
8. Verify that "Your device use" item is not present
9. Navigate to brave://settings/content/idleDetection
10. Verify that the page is empty.

example	example	example

Verify that the UI is not hidden when the feature is enabled:

1. Start Brave from the command line with --enable-features=IdleDetection
2. Repeat steps above, expect the reverse in the Verify steps.

example	example	example

[kjozwiak]

Verification PASSED on Samsung S10+ running Android 11 using the following build:

Nightly 1.32.44 Chromium: 94.0.4606.71

Case #1 - IdleDetection disabled

• checked https://idle-detection.glitch.me and ensured that the Idle Detection API is disabled
• verified that there's no UI associated with Idle Detection visible under Settings -> Site Settings
• verified that there's no UI associated with Idle Detection visible under Settings -> Site Settings -> All Sites

Example	Example	Example	Example

Case #2 - IdleDetection enabled

• launched Brave using --enable-features=IdleDetection
• ensured that visiting https://idle-detection.glitch.me allows you to enable the Idle Detection API
• ensured that enabling the Idle Detection API displays a permission modal
• ensured that Your device use appears under All Sites under Site Settings for https://idle-detection.glitch.me
• ensured disabling Idle Detection by removing --enable-features=IdleDetection removes the UI from All Sites

Example	Example