tests: better coverage in export song test

[theGreatWhiteShark]

cover

• different sample rates and sample depths
• different ADSR settings
• High pass and resonance filtering
• different layer selection algorithms
• stop notes
• notes with user-defined length
• auto stop note
• non-default pitch settings

addresses https://github.com/hydrogen-music/hydrogen/issues/1873

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This PR supersedes #1875. It removes the test using a sample depth of 8 since this one gives different results for Windows and Linux/macOS and it runs the tests on 32bit Windows too.