`seedWords` used to be stored on the metamask state temporarily at
certain points. This hasn't been the case since #5994, but references
to this state remained. All of the logic remained for correctly updating
these `seedWords`, handling them during navigation, and scrubbing them
from the state.
However the state was never updated in practice. The `seedWords` are
still returned by `verifySeedPhrase`, and they're still stored in
component state in a few places. But they aren't ever set in the Redux
metadata state or the Preferences controller.
All references to this state have been removed, along with any logic
for interacting with this state. A few unused actions were removed as
well.
* Move send to pages/
* Fix unit tests
* Finish UI
* Integrate asset dropdown to send actions
* Remove console.log
* Hide asset change during edit
* Enable switch from send token to seand eth
* Enable switching from token to eth when editing
* Fix linter
* Fixing test
* Fix unit tests
* Fix linter
* Fix react warning; remove console.log
* fix flat test
* Add metrics
* Address code review comments
* Consistent spacing between send screen form rows.
* Reduce height of gas buttons on send screen.
* Make send screen gas button height dependent on size of contents.
