[ENH] config: sort example workflows

[mw25]

Issue

Suggestion for biolab/orange-canvas-core#203

Description of changes

The tutorial entrypoints are sorted by name to make the order of the example workflows adjustable.
The entry point name for the default workflows starts with '000' so that they are at the beginning.
Unless the entrypoint name of another add-on starts with e.g. '!'
This way, example workflows could also be placed at the very beginning.
Normally the entrypoints are called 'exampletutorials' and are appended to the defaults. With a prefix ('100', '200') the order between different add-ons can be controlled.

The sorting could also be moved to orange-canvas-core/orangecanvas/application/examples.py, because the add-on-internal sorting is already there.

Includes

• Code changes
• Tests
• Documentation

[CLAassistant]

All committers have signed the CLA.

[codecov]

Codecov Report

Merging #5600 (f71c93e) into master (2146396) will increase coverage by 0.00%.
The diff coverage is n/a.

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+ Hits        56261    56262    +1     
+ Misses       9205     9204    -1