test: add unit test for non-standard "scriptsig-not-pushonly" txs

Summary:

The function IsStandardTx() returns rejection reason "scriptsig-not-pushonly"
if the transaction has at least one input for which the scriptSig consists of
any other ops than just PUSHs.

This is a a backport of Core PR17720

Test Plan: ninja && ninja check

Reviewers: #bitcoin_abc, majcosta

Reviewed By: #bitcoin_abc, majcosta

Subscribers: majcosta

Differential Revision: https://reviews.bitcoinabc.org/D8872