Make workflow dispatch checkbox from source into action (infra)

[Hook25]

Description

This refactors the Checkbox from source workflow into an action (that is now used by the workflow).

This also implements the following changes:

• Support for noprovision systems
• New launcher override parameter (for the action) to provide secrets/envvars/manifest overrides
• New zapper channel to specify the zapper snap to use

Resolved issues

I think this is satisfactory conclusing to this spike.

Fixes: https://warthogs.atlassian.net/browse/CHECKBOX-1583

Documentation

New parameter documented as the others in the action header

Tests

Run that executes the zapper-canary testplan dispatched with the following command:

gh workflow run dispatch_lab_job.yaml --ref action_checkbox -f 'matrix_to_create=[{"queue":"202203-30003","match":".*","test_plan":"com.canonical.certification::canary-zapper"}]'

https://github.com/canonical/checkbox/actions/runs/11106549363/job/30855120456

Final, post all commits/refactorings/landing version: https://github.com/canonical/checkbox/actions/runs/11144034945/job/30970401973