* refactor code for including available location providers

* fix test

Rename Piwik_TestingEnvironment to TestingEnvironment and move the class to Piwik\Tests\Framework namespace. Remove manual require statements.

Fix TrackerTest provideContainerConfig() method. Now that it is called during test case setup, check the const is defined before defining it. Otherwise, there will be an error regarding redefining the constant.

Refs #7632, when getting user info in UserCountry dimensions, set language using request object not visitor object, since the Country dimension will be triggered before the Lanuage one. Includes test.

In tracker, run scheduled tasks via CliMulti, add tests for running scheduled tasks through tracker including test that ensures tracker won't fail if scheduled tasks fail, allow tests to override container config by setting a property in the testing environment file, and properly use TestingEnvironment in RequestCommand.

added a new url parameter send_image=0 to disable sending an
image and instead response with a 204 code