fix: handle OR call for constant inputs

[ivokub]

Description

Handle api.Or in case either of the inputs is a constant without creating a constraint. Already handled this way in SCS.

Thanks to @wuestholz for reporting.

Type of change

• Bug fix (non-breaking change which fixes an issue)

Checklist:

• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• I did not modify files generated from templates
• golangci-lint does not output errors locally
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules