Summary:
Migrate the Circle CI configuration to the 2.1 schema and take advantage of new config reuse features.
I've enabled pipelines in the facebook/react-native Circle CI project, a requirement for Circle CI 2.1 features.
### Overview
* Use executors to provide a common set of execution environments.
* Use commands to provide reusable steps (running yarn with cache, installing Android dependencies, ...)
* Use parametrized commands/jobs to reuse job definitions for `test_js` and `test_js_lts` where the only difference is the version of node provided by the environment.
* Reduce total execution time by [storing the git repo in a cache as opposed to using workspaces](https://circleci.com/blog/persisting-data-in-workflows-when-to-use-caching-artifacts-and-workspaces/)
* Fix various flaky end-to-end test failures related to CocoaPods and the CLI.
* Move `analyze` job to `analysis` workflow and rename to `analyze_pr`
* Rename `test_javascript` as `test_js`.
* Split up end-to-end test job into `test_ios_e2e` and `test_js_e2e`.
## Changelog
[Internal] [Changed] - Migrate to Circle CI 2.1 and fix e2e tests
Pull Request resolved: https://github.com/facebook/react-native/pull/25036
Differential Revision: D15565515
Pulled By: hramos
fbshipit-source-id: cfba2154a9fdc96400cbf778bd5d13e9411ee3f8
171cc0edb7