[make:schedule] a new command for creating recurring Symfony Schedules

[jrushlow]

• adds a new make:schedule command

• creates stateful schedulers

• If Symfony/Scheduler is not already installed - rather than using an exit early strategy - we composer install symfony/scheduler. This is the "shift" MakerBundle is making to handling missing dependencies.

• We check any files in src/Message -> if files exist -> ask the user to select a message class to use with the new schedule. The "suggested name" of the new schedule is the filename of the message w/ the Message suffix removed.
  

• The user also has the ability to select "Empty Message" to create a new schedule regardless if any message were found. This will create a "empty" schedule.

• If no existing messages exist -> ask the user the name of the "empty" schedule we'll create
  

Empty Schedule:

Schedule from message:

[jrushlow]

This could be cool todo. Idea is in the choice list we have:
0 -> Empty Schedule
1 -> New Schedule
2 -> ...

But I can't remember if a) this is actually dooable to run a maker inside a maker without duplicating code && b) if there arn't any messages, or if symfony/messenger is not installed - what should we do...

[jrushlow]

We're going to skip this for now. Revisit at a later time...