Add end-to-end tests (apply, plan, destroy) for examples.
When run, `tests/examples_e2e`:
1. Create an environment for tests to run (folder, project vpc network)
2. For each marked example (with `e2e` tftest directive), run apply, plan, destroy
3. Verify:
* no failure in apply
* empty plan after apply
* no failure during destroy
4. When all tests are done, destroy test environment
More details in `tests/examples_e2e/README.md`
