WIP: backend/pkg/plugins: Add CheckHeadlampPluginVersion

[illume]

For checking plugin version compatibility.

WIP: This should only fail when run in-cluster mode, not in app mode. Because those delivering an app with bundled plugins would consider this an error if the in-cluster app ran without plugins.

How to test?

• there is a unit test
• add an old plugin (less than 0.8.0-alpha.10), and the backend should fail to run with an error explaining the problem
• it should NOT exit with an error when run in app mode
• it SHOULD exit with an error when run in-cluster mode

The backend should fail when in-cluster mode.

# checkout the previous release and install an old plugin
git checkout 
cd plugins/examples/pod-counter/
npm i
npm start

# running the backend should fail because old plugin
cd ../../../
make run-backend

Test the app should not error:

# checkout the previous release and install an old plugin
git checkout 
cd plugins/examples/pod-counter/
npm i
npm start

# running the app should NOT fail because of an old plugin
cd ../../../
cd app
npm start

[github-actions]

Backend Code coverage changed from 56.6% to 57.1%. Change: .5% 😃.

[github-actions]

Backend Code coverage changed from 56.3% to 57.1%. Change: .8% 😃.

[github-actions]

Backend Code coverage changed from 56.7% to 57.1%. Change: .4% 😃.