Hide UI elements related to IdleDetection

[pes10k]

Following up from #18269 (comment), Brave currently disables the Idle Detection API, but doesn't remove the UI elements / settings around it, causing confusion.

To prevent confusion, we should just hide the UI elements related to the Idle Detection API

[mkarolin]

QA verification steps (Desktop):

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.

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.

QA verification steps (Android):

STR/Cases can be found via brave/brave-core#10299 (comment).

[mkarolin]

Split out Android into a separate issue: #18414

[kjozwiak]

Going to change this from release-note/exclude --> release-notes/include as we're removing UI elements. @rebron @LaurenWags if you feel differently, please feel free to change it back 👍

[stephendonner]

Verified PASSED using

Brave	1.31.73 Chromium: 94.0.4606.71 (Official Build) beta (x86_64)
Revision	1d32b169326531e600d836bd395efc1b53d0f6ef-refs/branch-heads/4606@{#1256}
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

[srirambv]

Verification passed on Oppo Reno 5 with Android 11 running 1.31.81 x64 Beta build

Verified when IdleDetection there is no permission that is asked on site settings

• Verified visiting https://idle-detection.glitch.me, 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

Verified when IdleDetection enabled via command line args, site permission is requested and added to site settings

• Launched Brave using --enable-features=IdleDetection command line args
• Verified visiting https://idle-detection.glitch.me detects IdleDetection API being enabled
• Verified selecting the checkbox on the page presents Idle Detection API permission modal
• Verified Your device use appears under All Sites under Site Settings for https://idle-detection.glitch.me
• Verified disabling Idle Detection by removing --enable-features=IdleDetection removes the UI from All Sites

---

Verification passed on Samsung Tab A with Android 10 running 1.31.81 x64 Beta build

Verified when IdleDetection there is no permission that is asked on site settings

• Verified visiting https://idle-detection.glitch.me, 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

Verified when IdleDetection enabled via command line args, site permission is requested and added to site settings

• Launched Brave using --enable-features=IdleDetection command line args
• Verified visiting https://idle-detection.glitch.me detects IdleDetection API being enabled
• Verified selecting the checkbox on the page presents Idle Detection API permission modal
• Verified Your device use appears under All Sites under Site Settings for https://idle-detection.glitch.me
• Verified disabling Idle Detection by removing --enable-features=IdleDetection removes the UI from All Sites