Trigger machine error checking during startup. Otherwise slicing often randomly fails.

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Description

Cura slicing hangs fails randomly, all just because printers are initialized before MachineErrorChecker (on which slicing depends) and the asynchronous checks never trigger as the checker stays in faulty initial state.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Printer definition file(s)
• Translations

How Has This Been Tested?

• Run cura, configure printer. close. run cura, try to silce (it will use the previously configured printer). it hangs for quite a long time, then gives unspecified error on every slicing.

Test Configuration:

• Operating System:

Checklist:

• My code follows the style guidelines of this project as described in UltiMaker Meta and Cura QML best practices
• I have read the Contribution guide
• I have commented my code, particularly in hard-to-understand areas
• I have uploaded any files required to test this change