IDEA-108599 Gradle: Integrate 'run task' to the ide execution system

Use dummy psi file for external task location in order to avoid applying standard IJ groovy script runners to the build.gradle tasks
IDEA-108599 Gradle: Integrate 'run task' to the ide execution system

1. Provide ability to re-use existing run configurations;
2. Use different text for running single and multiple tasks;
SPI: do not force file type association for provider configuration files
SPI: initial language support
SPI: initial checks