Change unstoppable domains user opt-in interstitial from Cloudflare DoH to ethereum option

[yrliou]

We're soon retiring DoH option, so we should use ethereum option in the interstitial for user onboarding.

Interstitial was first introduced by brave/brave-core#7702.

[yrliou]

We would like to do the same for ENS too.

[srirambv]

Brave	1.40.80 Chromium: 102.0.5005.78 (Official Build) beta (64-bit)
Revision	df6dbb5a9fd82af3f567198af2eb5fb4876ef99c-refs/branch-heads/5005_59@{#3}
OS	☑️ Linux	☑️ Windows 11 Version 22H2 (Build 22621.1)	☑️ macOS Version 12.0.1 (Build 21C52)
Verified steps from brave/brave-core#13256 Verified when method to resolve is set to Ask, interstitial page is shown Verified selecting proceed on interstitial page, sets method to resolve to Ethereum
.crypto domain	22148.crypto.-Linux.mp4	22148.crypto.-Windows.mov	22148.crypto.-macOS.mov
.eth domain	22148.eth.-Linux.mp4	22148.eth.-Windows.mov	22148.eth.-macOS.mov

[srirambv]

Verification passed the following devices running 1.40.101 x64 build

• Verified steps from brave/brave-core#13256
• Verified when method to resolve is set to Ask, interstitial page is shown
• Verified selecting proceed on interstitial page, sets method to resolve to Ethereum

Oppo Reno 5 (Android 12)

.crypto domain	.eth domain
22148.crypto-ARM.mp4	22148.eth-ARM.mp4

Samsung Tab A (Android 10)

.crypto domain	.eth domain
22148.crypto-Tab.mp4	22148.eth-Tab.mp4