Implement compatible_installer

[NeoTheThird]

for ubports/ubports-installer#2509

[NeoTheThird]

Alright, this has gotten interesting! I finally looked into writing ajv plugins for more advanced schema validations. this now allows us to specify a ubports_installer-compatibility semver range in the schema of every action and to validate that the compatible_installer semver range specified on an operating_system of a device config is a subset of this. Straightforward syntax, straightforward validation.

The scaffolding of this plugin can be used to do much more validation later, very excited to see where this will go!