feat(jest): report test files and test positions

[nicojs]

Report the test file names and test positions from the jest-runner plugin back to the main process. They will end up in your JSON report in line with the latest mutation-testing-report-schema changes: stryker-mutator/mutation-testing-elements#786

For example:

  "testFiles": {
    "src/sum.test.js": {
      "tests": [
        {
          "id": "0",
          "name": "adds 1 + 2 to equal 3",
          "location": {
            "start": {
              "column": 2,
              "line": 3
            }
          }
        },
        {
          "id": "1",
          "name": "sub 1 - 0 to equal 1",
          "location": {
            "start": {
              "column": 2,
              "line": 6
            }
          }
        }
      ],
      "source": "const {sum, sub} = require('./sum');\n\ntest('adds 1 + 2 to equal 3', () => {\n  expect(sum(1, 2)).toBe(3);\n});\ntest('sub 1 - 0 to equal 1', () => {\n  expect(sub(1, 0)).toBe(1);\n});\n"
    }
  },

[simondel]

@nicojs Could you explain why you want this change?

[nicojs]

Sure.

Each test runner can now optionally also report the file names and test locations. If they are provided, then Stryker will also report them to the mutation testing report JSON. We're adding support to display that information with stryker-mutator/mutation-testing-elements#865