recognize bare multisigs as standard only when using minimal pushes

Summary:
Since we're adopting SCRIPT_VERIFY_MINIMALDATA as a hard consensus rule, it doesn't make sense to allow "spendable" but actually unspendable outputs as standard.

While we're adding tests for this, also test some other nonminimal forms of standard outputs.

Depends on D3872

Test Plan: make check

Reviewers: deadalnix, jasonbcox, Fabien, #bitcoin_abc

Reviewed By: jasonbcox, Fabien, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D3865