Ftrack: Handle missing published path in integrator

[iLLiCiTiT]

Brief description

Ftrack integrator can handle if published_path is not filled on representation.

Description

Ftrack integrator expected that published_path is always filled on representation for review and thumbnail upload, but in some very specifici cases they may not be integrated with IntegrateAsset thus they don't have filled the key at all. But in that cases can be used their source path.
Before this PR it crashed with KeyError.

Traceback

Traceback (most recent call last):
   File "C:\Program Files (x86)\OpenPype\dependencies\pyblish\plugin.py", line 522, in __explicit_process
     runner(*args)
   File "C:\Program Files (x86)\OpenPype\openpype\modules\ftrack\plugins\publish\integrate_ftrack_instances.py", line 273, in process
 KeyError: 'published_path'

Testing notes:

Not sure how it is possible to make reviewable that is not integrated to validate it won't crash.

1. Run publish that should integrate at lease review or thumbnail to ftrack
2. Validate they are integrated

[ynbot]

Task linked: OP-3644 Handle missing published path in ftrack integrator