Start remote binary using env and appling ephemeral volume

[AndrienkoAleksandr]

What does this PR do?

At this pr I changed a bit model: applied Type field to the model.ChePlugin

Inject remote endpoint binary using env variable with remote binary path and volume where is binary located.
For this purpose we are using init container from che-theia editor-plugin:

initContainers:
  - name: remote-runtime-injector
    image: aandrienko/che-theia-endpoint-runtime-binary:next
    volumes:
      - mountPath: "/remote-endpoint"
        name: remote-endpoint
        ephemeral: true
    env:
      - name: PLUGIN_REMOTE_ENDPOINT_EXECUTABLE
        value: /remote-endpoint/plugin-remote-endpoint
      - name: REMOTE_ENDPOINT_VOLUME_NAME
        value: remote-endpoint

Plugin broker should find this init container by name remote-runtime-injector and only for che-theia editor plugin. Then plugin-broker should analize env variables and volume from init container.

REMOTE_ENDPOINT_VOLUME_NAME env we are using to find one volume which should be shared with other sidecar containers. In this volume init container on start should copy remote binary

PLUGIN_REMOTE_ENDPOINT_EXECUTABLE env will be shared with all sidecar containers.

To start remote binary in the sidecar container, plugin writer should define in the sidecar dockerfile ENTRYPOINT:

FROM some-image 
....
ENTRYPOINT ${PLUGIN_REMOTE_ENDPOINT_EXECUTABLE} 

Or apply starting remote binary in the entrypoint.sh script, if plugin image uses such one.

What issues does this PR fix or reference?

eclipse-che/che#13387

[codecov]

Codecov Report

Merging #76 into master will increase coverage by 0.97%.
The diff coverage is 81.15%.

@@            Coverage Diff             @@
##           master      #76      +/-   ##
==========================================
+ Coverage   67.17%   68.15%   +0.97%     
==========================================
  Files           6        7       +1     
  Lines         591      650      +59     
==========================================
+ Hits          397      443      +46     
- Misses        168      176       +8     
- Partials       26       31       +5

Impacted Files	Coverage Δ
brokers/unified/broker.go	83.51% <100%> (+0.26%)	⬆️
brokers/unified/vscode/broker.go	74.21% <100%> (+0.13%)	⬆️
brokers/unified/vscode/sidecar.go	100% <100%> (ø)	⬆️
brokers/unified/remote_runtime_injector.go	76.78% <76.78%> (ø)

---

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[benoitf]

IMHO description of the PR should tell the name of the env variable, what to add, etc.
Why it's like that, what we can do, with an example, etc.

[nickboldt]

What is the impact on docs for this change? #definitionOfDone

[amisevsk]

Typo: RemoteEndPointExecutableEnvVar

[amisevsk]

We shouldn't fail silently here.

[amisevsk]

If err == nil and runtimeBinaryPathEnv.Value == "", this will return nil, nil.

[AndrienkoAleksandr]

Fixed

[AndrienkoAleksandr]

IMHO description of the PR should tell the name of the env variable, what to add, etc.
Why it's like that, what we can do, with an example, etc.

Fixed

[AndrienkoAleksandr]

Closed on favor full solution #75
@amisevsk all your comments I handled using cherry-pick commits to #75