Expose send web UI on Android

[simoarpe]

Expose brave://wallet/send as a web UI on Android. Similarly to the Desktop version.
We don't want to expose the whole brave://wallet though, just the swap page.

[srirambv]

Verification passed on the following devices running 1.58.117 x64 build

• Verified steps from brave/brave-core#18984
• Verified Send UI is opened in a new tab
• Verified able to submit a send transaction
• Verified able to directly navigate to Send UI when wallet is created and unlocked

Oppo Reno 5 (Android 13)	Lenovo Tab (Android 12)
31260-ARM.mp4	31260-Tab.mp4