Add testnet status.cash seeder to chainparams

Summary:
status.cash provides some network monitoring services and operates public seeders
as part of its infrastructure. The testnet seeder has been crawling since October.

Test Plan:

ninja check
dig testnet-seeder.status.cash

Reviewers: O1 Bitcoin ABC, #bitcoin_abc, Mengerian

Reviewed By: O1 Bitcoin ABC, #bitcoin_abc, Mengerian

Subscribers: Mengerian

Differential Revision: https://reviews.bitcoinabc.org/D10620