Clean up `test_coverage_table_spec` file

Use more mock data in the test coverage table
spec file. Also refactor how we handle mock
apollo queries.

ee/spec/frontend/analytics/repository_analytics/components/mock_data.js

+export const defaultTestCoverageTable = {
+  allCoverageData: [],
+  allProjectsSelected: false,
+  hasError: false,
+  isLoading: false,
+  projectIds: {},
+};
+
+export const projects = [
+  {
+    fullPath: 'test/test',
+    name: 'test',
+    id: 1,
+    repository: {
+      rootRef: 'master',
+    },
+    codeCoveragePath: '#',
+    codeCoverageSummary: {
+      averageCoverage: '1.45',
+      coverageCount: '1',
+      lastUpdatedOn: '2021-01-30T20:34:14.302Z',
+    },
+  },
+];