Enable SNS feature flag by default and update opt-in page

[yrliou]

Once we switch to another provider that can support all RPC calls needed for SNS, we can enable the feature by default and update the opt-in page to specify the provider and link to its ToU and privacy policy.
cc @jamesmudgett

Security and privacy review was already done in https://github.com/brave/security/issues/1099.
Main PRs for the feature: brave/brave-core#15617, brave/brave-core#15863
Wallet address resolution UI on Android was done in brave/brave-core#16423.

[kjozwiak]

The above requires 1.49.92 or higher for 1.49.x verification 👍

[srirambv]

Verification passed on the following devices running 1.49.106 x64 build

• Verified steps from brave/brave-core#17034
• Verified SNS feature is enabled by default and set to Ask
• Verified entering a .sol domain in omnibox shows SNS Interstitial page
• Verified Disable sets SNS feature to Disabled
• Verified Proceed with Syndica Server sets SNS feature to Enabled
• Verified entering onybose.sol and ironpaw.sol in Send to field resolves the address

Oppo Reno 5 (Android 13)	Samsung Tab A (Android 10)
28282-ARM.mp4	28282-Tab.mp4

[srirambv]

Verification passed on

Brave	1.49.108 Chromium: 110.0.5481.104 (Official Build) beta (64-bit)
Revision	46de4a7f41979e829b430bc1ee30ef483aa227ac-refs/branch-heads/5481_77@{#19}
OS	Linux

• Verified steps from brave/brave-core#17034
• Verified SNS feature is enabled by default and set to Ask
• Verified entering a .sol domain in omnibox shows SNS Interstitial page
• Verified Disable sets SNS feature to Disabled
• Verified Proceed with Syndica Server sets SNS feature to Enabled
• Verified entering onybose.sol and ironpaw.sol in Send to field resolves the address

28282.mp4

---

Verification passed on

Brave	1.49.108 Chromium: 110.0.5481.104 (Official Build) beta (64-bit)
Revision	46de4a7f41979e829b430bc1ee30ef483aa227ac-refs/branch-heads/5481_77@{#19}
OS	Windows 11 Version 22H2 (Build 22621.755)

• Verified steps from brave/brave-core#17034
• Verified SNS feature is enabled by default and set to Ask
• Verified entering a .sol domain in omnibox shows SNS Interstitial page
• Verified Disable sets SNS feature to Disabled
• Verified Proceed with Syndica Server sets SNS feature to Enabled
• Verified entering onybose.sol and ironpaw.sol in Send to field resolves the address

28282.mp4

---

Verification passed on

Brave	1.49.108 Chromium: 110.0.5481.104 (Official Build) beta (arm64)
Revision	46de4a7f41979e829b430bc1ee30ef483aa227ac-refs/branch-heads/5481_77@{#19}
OS	macOS Version 13.0 (Build 22A380)

• Verified steps from brave/brave-core#17034
• Verified SNS feature is enabled by default and set to Ask
• Verified entering a .sol domain in omnibox shows SNS Interstitial page
• Verified Disable sets SNS feature to Disabled
• Verified Proceed with Syndica Server sets SNS feature to Enabled
• Verified entering onybose.sol and ironpaw.sol in Send to field resolves the address

28282.mov