run_task to enable running multiple tasks

[sagiegurari]

Features Description
run_task today only supports running a single task.
as a preparation for #323 it should also support running a list of tasks.

Code Sample

run_task = [
    { name = "single-task", condition = { channels = ["nightly"] } },
    { name = ["task1", "task2] }
]

Having the name attribute in this scenario to also accept a list of names, we can have it run multiple tasks.
later on in #323 we can add the parallel attribute into this object to support parallel invocation of those tasks.