Update seed and seed selection

Summary:
Restore the limit of seeds per ASN.
Restore requirement in term of uptime.
Include bitprim nodes.
Include bcash nodes.

Test Plan: Boostrap a node, ensure it connects successfully to the network.

Reviewers: #bitcoin_abc, schancel

Reviewed By: #bitcoin_abc, schancel

Subscribers: teamcity

Differential Revision: https://reviews.bitcoinabc.org/D1745