[Test suite] Exhaustively test PSBTParser with all supported script types

[kdmukai]

Description

Creates a test structure to exhaustively test the PSBTParser against all supported script types in every conceivable combination in the most DRY way possible.

Adds the PSBTTestData class: contains predefined PSBT input and output snippets for all supported single-signature and multisig script types. These snippets can be mixed and matched as needed for the exhaustive tests. Resides in its own class so that other tests can potentially re-use the test data.

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This pull request is categorized as a:

• Other: Test suite enhancement / additional tests

Checklist

• I’ve run pytest and made sure all unit tests pass before sumbitting the PR

If you modified or added functionality/workflow, did you add new unit tests?

• Yes

I have tested this PR on the following platforms/os:

• Other: Test suite runs in CI or in local dev but generally not on the device.