Rename Jest configuration files

The following discussion from !56133 (merged) should be addressed:

• @vitallium started a discussion:

  I wonder if we should rename our Jest config files so they always end with config.js to match them easily.

  1. jest.config.base.js -> jest.base.config.js
  2. jest.config.integration.js -> jest.integration.config.js

  /cc @pslaughter