Refactoring tight coupling between Song and SongParser

[twollgam]

What does this PR do?

The tight coupling between Song and SongParser will be broken. A very simple interface is used.

Closes Issue(s)

None

Motivation

This will help in upcoming prs to create unit tests more easy.

[github-actions[bot]]

Download the artifacts for this pull request:

• Performous-1.2.0-870-5fe8250-alpha.AppImage.zip
• Performous-1.2.0-870-5fe8250-alpha.dmg.zip
• Performous-1.2.0-870-5fe8250-alpha-debian_10.deb.zip
• Performous-1.2.0-870-5fe8250-alpha-debian_11.deb.zip
• Performous-1.2.0-870-5fe8250-alpha-fedora_35.rpm.zip
• Performous-1.2.0-870-5fe8250-alpha-fedora_36.rpm.zip
• Performous-1.2.0-870-5fe8250-alpha-fedora_37.rpm.zip
• Performous-1.2.0-870-5fe8250-alpha-fedora_38.rpm.zip
• Performous-1.2.0-870-5fe8250-alpha-mingw-w64.exe.zip
• Performous-1.2.0-870-5fe8250-alpha-msvc.exe.zip
• Performous-1.2.0-870-5fe8250-alpha-ubuntu_20.04.deb.zip
• Performous-1.2.0-870-5fe8250-alpha-ubuntu_22.04.deb.zip

This service is provided by nightly.link. These artifacts will expire in 90 days and will not be available for download after that time.

[ooshlablu]

Tested with singing on Ubuntu 20.04 with both the deb and AppImage, didn't notice any issues.