Concatenate output of tasks for sub-projects and root project tasks

[vvvlasov]

Turns out gradle tasks --all only returns tasks for sub-projects and default tasks for multi-project setup. In order to get autocompletion for root project tasks this has to be concatenated with gradle tasks which returns the root project tasks but no sub-project tasks. This is what I see in my repo

vvlasov@mac monorepo-demo % gradle --console=plain tasks | grep integration
integrationTest - Runs integration tests.
vvlasov@mac monorepo-demo % gradle --console=plain tasks --all | grep integration
project-1:integrationTest - Runs integration tests.
project-2:integrationTest - Runs integration tests.
project-3:integrationTest - Runs integration tests.