feat: support runs-on labels and group

[raffis]

Current situation

act does not work with our worklfow declarations which are as follow:

  build:
    runs-on:
      labels:
        - generic-v2

acts runs-on only supports a string or or a string slice. However the github workflow schema does support group and labels keys.
See https://github.com/SchemaStore/schemastore/blob/master/src/schemas/json/github-workflow.json#L703-L721 for reference.

Proposal

This pr actually supports this use case. It will just combine labels and optional group declarations in the runs on output slice. This should be suitable for cover use cases for custom images targeting these labels.

[raffis]

Any update on this?

[codecov]

Codecov Report

Merging #2062 (36a53c8) into master (4989f44) will increase coverage by 0.36%.
Report is 271 commits behind head on master.
The diff coverage is 60.01%.

@@            Coverage Diff             @@
##           master    #2062      +/-   ##
==========================================
+ Coverage   61.22%   61.58%   +0.36%     
==========================================
  Files          46       53       +7     
  Lines        7141     8807    +1666     
==========================================
+ Hits         4372     5424    +1052     
- Misses       2462     2951     +489     
- Partials      307      432     +125     

Files	Coverage Δ
pkg/common/executor.go	51.69% <100.00%> (+1.69%)	⬆️
pkg/container/docker_cli.go	82.23% <ø> (ø)
pkg/container/docker_logger.go	52.08% <ø> (ø)
pkg/runner/step_action_local.go	93.54% <100.00%> (ø)
pkg/runner/step_action_remote.go	91.56% <100.00%> (+0.65%)	⬆️
pkg/runner/step_docker.go	93.18% <100.00%> (ø)
pkg/container/file_collector.go	37.30% <0.00%> (ø)
pkg/container/util.go	0.00% <0.00%> (ø)
pkg/container/docker_build.go	60.00% <80.00%> (+1.02%)	⬆️
...ontainer/linux_container_environment_extensions.go	23.07% <0.00%> (-1.25%)	⬇️
... and 31 more

... and 2 files with indirect coverage changes

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[ChristopherHX]

Thank you for implementing this,
Yes act should support this, but another maintainer or the owner need to approve too