[native] Add SIWEPanel to ConnectEthereum screen

Summary:
See designs. Note that this experience is still a little "rough around the edges"... proper loading state and making sure the bottom sheet is outside of the SafeAreaView will happen in later diffs.

Depends on D7843

Test Plan:

Reviewers: atul, ginsu

Reviewed By: atul

Subscribers: tomek

Differential Revision: https://phab.comm.dev/D7844