[Cashtab] Change route and component for SendToken to Token

Summary:
T3528

This is no longer really a "SendToken" component. Send is one of many token actions available.

Going forward, will eventually support loading any token at this route. Some unsupported tokens will not have available actions.

Token is a more appropriate name. Update the component name and the route. Continue to support the legacy 'send-token' route in case someone direct navigates. Move from "components/Send/" to "components/Etokens/"

Test Plan: npm test

Reviewers: #bitcoin_abc, emack

Reviewed By: #bitcoin_abc, emack

Differential Revision: https://reviews.bitcoinabc.org/D15992