add GPC for iOS

[diracdeltas]

for parity with https://github.com/brave/brave-browser/issues/32231

[anthonypkeane]

@iccub Lets try get this into 1.62

[hffvld]

Verified on iPhone 14 using version(s):

Device/OS: iPhone 14 / iOS 17.3
Brave build: 1.62 (24.1.9.23)
BraveCore: 1.62.128 (120.0.6099.144)

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STEPS:

1. Launch Brave
2. Three-dot menu > Settings > Brave Shields & Privacy
3. Find Enable Global Privacy Control > Verify
4. Close the settings and go to any website, for example, Wikipedia
5. In Safari on the Desktop open Web Inspector > Console
6. Paste the query navigator.globalPrivacyControl > Enter > Verify the response result
7. Now disable Enable Global Privacy Control in Brave settings > Refresh the opened webpage
8. In the Console paste the query navigator.globalPrivacyControl again > Enter > Verify the response result
9. Now go to https://global-privacy-control.glitch.me/ which was used to verify the same issue on Desktop and Android
10. Check the Client-side detection section when Enable Global Privacy Control is ON > Verify
11. Now disable Enable Global Privacy Control > Refresh the page https://global-privacy-control.glitch.me/ > Verify

ACTUAL RESULTS:

• Verified that Enable Global Privacy Control is enabled by default
• Verified that in the Console:
  • navigator.globalPrivacyControl shows true when Enable Global Privacy Control is ON
  • navigator.globalPrivacyControl shows false when Enable Global Privacy Control is OFF
• Verified that https://global-privacy-control.glitch.me/ shows the correct results:
  • When Enable Global Privacy Control is ON, Client-side detection shows navigator.globalPrivacyControl: true
  • When Enable Global Privacy Control is OFF, Client-side detection shows navigator.globalPrivacyControl: false

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