Remove legacy BSQ altcoin trading

[jmacxx]

Fixes #7011 requested by @refund-agent2

• ~remove~filter legacy BSQ altcoin accounts.
• disallow creating legacy BSQ altcoin accounts.
• BSQ altcoin offers cannot be created because there would be no BSQ altcoin accounts.
• filter out legacy BSQ altcoin offers from market offer book / views.
• BSQ altcoin offers cannot be taken because they would be filtered out from the market.

[ghost]

@alvasw pls review.