test: add unit test for non-standard "scriptsig-not-pushonly" txs
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 [[ https://github.com/bitcoin/bitcoin/pull/17720 | PR17720 ]]

Test Plan: `ninja && ninja check`

Reviewers: #bitcoin_abc, majcosta

Reviewed By: #bitcoin_abc, majcosta

Subscribers: majcosta

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

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