Task support for ij macro language

[NicoKiaru]

This PR adds the class net.imagej.legacy.task.TaskHelper which allows to use Tasks in the IJ1 macro language via the call function.

Demo scripts are provided for Tasks in the macro language and in the groovy language, with or without cancellation handling.

To enable the use of Task in the ij macro language all Tasks are stored in the ObjectService while they are not finished.

See forum post https://forum.image.sc/t/demo-and-proposal-new-progress-bars-for-fiji/64956/10 for context about the need

[NicoKiaru]

My concerns for the review:

• is the static initialisation of the ObjectService, LogService and TaskService ok ?
• should I write tests ? How should they look like ?
• In the TaskWithCancel.ijm example script, the function taskIsCanceled is a bit weird: it is converting a String ("true", "false") into a number (0,1) that acts as a Boolean. Is there a better way ? Can I directly return a Boolean in TaskHelper#isCanceled ?

[NicoKiaru]

Make a test that is a macro and that uses each functions of Tasks

[NicoKiaru]

• In the TaskWithCancel.ijm example script, the function taskIsCanceled is a bit weird: it is converting a String ("true", "false") into a number (0,1) that acts as a Boolean. Is there a better way ? Can I directly return a Boolean in TaskHelper#isCanceled ?

I need to test it