MDL-41421 tool_generator: Import .jmx template

Ideally we should generate all the XML based on
modular components so we can also switch templates
between different sizes, this is a first step and
more work should be done in future in this direction.
MDL-41421 tool_generator: Adding a test plan generator to feed JMeter

Also changing course_backend.php coding style
according to codechecker.
MDL-41421 tool_generator: Adding a CLI tool to generate the test plan