Indicate when paid usernames will expire

[markmhendrickson]

Currently there's no way for a user to see how long they have until usernames associated with their accounts will expire.

We should indicate this somewhere in the UI so it's clear.

Related to #465

[friedger]

.id names start to expire in 4-6 months (stx block 50,000)

[markmhendrickson]

I presume expiration blocks per name should be relatively simple to query and display. Perhaps we could add an option directly into the wallet UI that triggers a configured transaction for renewing the name via transaction signing, with or without an option to adjust the time period for renewal.

@andresgalante we may need to tackle this in Q1 given the timeline indicated by @friedger above, at least a month or so before names that were migrated for Stacks 2.0 start to expire.