* Moving examples to the page for retrieving runtime fields.
* Adding runtime_mappings to request body of search API.
* Updating runtime_mappings properties and adding runtime fields to search your data.
* Updating examples and hopefully fixing build failure.
* Fixing snippet formatting that was causing test failure.
* Adding page in Painless guide for runtime fields.
* Fixing typo.
Co-authored-by: Elastic Machine <elasticmachine@users.noreply.github.com>