feat: run all app e2e tests when configuring new sub apps

[MitchellCash]

When a new SubApp is added to a project the project is now configured to run all E2E tests by default. Currently it only runs the main app E2E tests.

Closes #1167.

PR Checklist

Please check if your PR fulfills the following requirements:

• [x] The commit message follows our guidelines: https://github.com/nestjs/nest/blob/master/CONTRIBUTING.md
• [x] Tests for the changes have been added (for bug fixes / features)
• [ ] Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

• [ ] Bugfix
• [x] Feature
• [ ] Code style update (formatting, local variables)
• [ ] Refactoring (no functional changes, no api changes)
• [ ] Build related changes
• [ ] CI related changes
• [ ] Other... Please describe:

What is the current behavior?

Issue Number: #1167

What is the new behavior?

It will now create a new jest-e2e.json file in the ./apps root directory containing references to each sub apps E2E test configs.

{
  "projects": [
    "apps/app-one/test/jest-e2e.json",
    "apps/app-two/test/jest-e2e.json",
    "apps/app-three/test/jest-e2e.json",
    "apps/app-four/test/jest-e2e.json"
  ]
}

And updating the the test:e2e to now run jest --config apps/jest-e2e.json

Does this PR introduce a breaking change?

• [ ] Yes
• [x] No

Other information

@kamilmysliwiec this differs from the open issue slightly because as I was testing on my own monorepo with 3 sub apps, the package.json test:e2e script would come out rather long and not scalable:

"test:e2e": "jest --projects ./apps/my-app/test/jest-e2e.json ./apps/my-other-app/test/jest-e2e.json ./apps/my-different-app/test/jest-e2e.json"

So instead I opted for a dedicated jest-e2e.json that references all the different project configs.

Appreciate any and all feedback!

[MitchellCash]

I should also add - why not just make the contents of ./apps/jest-e2e.json use regex to find all the spec files and remove the config from each app.

./apps/jest-e2e.json could look like this and do the same job with less Jest config files:

{
  "moduleFileExtensions": ["js", "json", "ts"],
  "rootDir": ".",
  "testEnvironment": "node",
  "testRegex": ".e2e-spec.ts$",
  "transform": {
    "^.+\\.(t|j)s$": "ts-jest"
  }
}

I decided against this because I am not sure how NestJS users modify their jest-e2e.json config per sub app. If you would prefer this approach please let me know.