Implement typescript support

[spalger]

Closes #18780

This PR enables TypeScript support in both the server and the client. Here is a summary of how this works:

• distributable
  • does not have any capacity to run TypeScript
  • all TS transpilation must happen at build time before shipping distributable
• building
  • .ts and .tsx files are converted to .js
  • Full type-check is run while TS is transpiled into .js
  • **/*.ts, **/*.tsx, **/*.d.ts and **/tsconfig.json files are stripped from the build after successful compilation
• plugin helpers
  • plugins with a tsconfig.json file at their root will be transpiled and have TS files stripped while building
• development
  • ts-node added to babel-register to auto-transpile .ts files in the server/jest/mocha
  • ts-loader transpiles .ts and .tsx files in webpack (without checking types)
  • Editor integrations provide type-checking feedback to developers (vscode, atom, vim, webstorm)
  • node scripts/tslint lints all typescript projects with tslint
  • pre-commit hook lints modified .ts, .tsx, and .d.ts files (just like .js files)

notes:

• node scripts/tslint can take specific files/globs as arguments to focus on those files, and/or a --project path/to/tsconfig.json flag to focus on files associated with a specific tsconfig.json file.
• Rather than "linting all typescript files" we "lint all typescript projects", which are defined with tsconfig.json files.

  kibana/src/dev/tslint/projects.ts

  Lines 11 to 17 in a5b4512

  	const PROJECT_PATHS = [
  	require.resolve('../../../tsconfig.json'),
  	require.resolve('../../../x-pack/tsconfig.json'),
  	require.resolve('../../../packages/kbn-dev-utils/tsconfig.json'),
  	require.resolve('../../../packages/kbn-pm/tsconfig.json'),
  	require.resolve('../../../packages/kbn-system-loader/tsconfig.json'),
  	];

  is the master list of tsconfig files, so we don't have to go searching for them all the time. By linting "projects" instead of individual files we allow the use of type-enabled linting rules, like https://palantir.github.io/tslint/rules/no-unused-variable
• Once babel 7 is released we will remove ts-node/ts-loader and just transform TS to JS with babel

[spalger]

I'm going to break this up a bit and resubmit without all this noise from @elasticmachine

[elasticmachine]

💔 Build Failed

• continuous-integration/kibana-ci/pull-request