Add support of dockerimage tool in Devfile

[sleshchenko]

What does this PR do?

The main purpose of this PR is adding support of dockerimage tool in Devfile.

But it also contains the following Devfile API improvements:

1. Improve devfile.json:

• Deny additional properties for Tool;
• Make tool implementation specific fields required accordingly to type value;
• Limit actions number in command to 1 item since we don't support more yet;

2. Add testing of Devfile JSON Schema. It allows us to guarantee that no any restrictions are broken because of a typo in devfile.json or validator implementation we use (I faced an issue that we declare our devfile.json as JSON Spec 07 Draft but validator that we use don't support if/then/else statements and just skip them.
   It also allows seeing an error message that is thrown by a validator in the source code, like instance failed to match exactly one schema (matched 0 out of 3) when chePlugin tool does not have id required field. It is a definitely confusing message and we should consider rewriting devfile.json/use another validator/customize current one to make a message more clear.

As an example of che-in-che Devfile with dockerimage

Che-in-Che Devfile with dockerimage tool used

specVersion: 0.0.1
name: che-in-che
projects:
  - name: che
    source:
      type: git
      location: 'https://github.com/eclipse/che.git'
tools:
  - name: theia-editor
    type: cheEditor
    id: org.eclipse.che.editor.theia:1.0.0
  - name: exec-plugin
    type: chePlugin
    id: che-machine-exec-plugin:0.0.1
  - name: che-dev
    type: dockerimage
    image: eclipse/che-dev:nightly
    env:
      - name: TEST_ENV_VAR
        value: -\_-_-_/-
    endpoints:
      - name: tomcat
        port: 8080
        attributes:
          public: 'true'
    volumes:
      - name: maven
        containerPath: /home/user/.m2
    memoryLimit: 1536M
    mountSources: true
commands:
  - name: build
    actions:
      - type: exec
        tool: che-dev
        command: cd /projects/che && mvn -Pnative clean install
        workdir: /projects/che

To test changes the following link might be used {CHE_HOST}/f?url=https://github.com/sleshchenko/che/tree/dockerimage-che-in-che

What issues does this PR fix or reference?

#12389

Release Notes

Added support of dockerimage tool in Devfile. It allows defining one container tool much easier than using other tools types. The detailed description of Devfile format see https://redhat-developer.github.io/devfile.

Docs PR

I think devfile.json contains all the needed changes.

[sleshchenko]

@mshaposhnik I've fixed/answered your comments and added an ability to export workspace with dockerimage recipe. Please review again.

[sleshchenko]

ci-test

[che-bot]

Results of automated E2E tests of Eclipse Che Multiuser on OCP:
Build details
Test report
docker image: eclipseche/che-server:12649
https://github.com/orgs/eclipse/teams/eclipse-che-qa please check this report.

[sleshchenko]

Success Rate: 99.369% 🎉
@eclipse/eclipse-che-qa Please review #12649 (comment)