Provide option to receive info regarding if a task can be run inside a package

[amang034]

This task is linked to microsoft/lage#104.

Currently lage only gives a package graph and task graph separately, so task-scheduler doesn't know when some packages do not contain the tasks in the package.json.

Because of how the final combined package-task is generated, we might over-aggressively run tasks because of this missing info.

For example, if A depends on B and B depends on C:

A -> B -> C

and if only C has the task of special-C-build, when this following is called:

lage special-C-build --scope A

Nothing should be run because "A" doesn't have that task. The expected result is that nothing is run.

This task is to modify the api to accept the info for if a task can be run inside package