Support config argument on apps restart

[grgar]

• Fix fly -c <config.toml> apps restart doesn't pick up app name #4279

 Restart an application. Perform a rolling restart against all running Machines.
 
 Usage:
-  fly apps restart <app name> [flags]
+  fly apps restart [name] [flags]
 
 Flags:
+  -a, --app string           Application name
+  -c, --config string        Path to application configuration file
       --force-stop           Performs a force stop against the target Machine
   -h, --help                 help for restart
       --skip-health-checks   Restarts app without waiting for health checks

[dangra]

what for?

[grgar]

Seems odd some commands support it and some don't. I regularly use -c with other commands. While not personally on this one, that there is a bug report means someone else does so I thought I'd take a look.

edit: NameFromContext is already called if one is not specified on the command line, so update the usage to clarify that it is optional and support the normal app flag.