Improve doctests - conditional dependency skip

[Borda]

🚀 Feature

use conditional skip for doctest which are showing metrics with additional dependency
Thx @ethanwharris for finding this nice pytest extension - pytest-doctestplus
see sample usage: https://github.com/astropy/pytest-doctestplus#doctest-dependencies

Motivation

have all doctests/examples tested again

Pitch

At this moment we are skipping all which are not pure PyTorch so the outputs could be wrong after several changes in codebase

Alternatives

Additional context

[ethanwharris]

This is how we do it in Flash:

# Skip doctests if requirements aren't available
if not _IMAGE_AVAILABLE:
    __doctest_skip__ = ["ImageClassificationData", "ImageClassificationData.*"]

Then enable pytest-doctestplus in setup.cfg with doctest_plus = enabled.

Note: As doctests are not run by sphinx, the .. doctest-requires:: asdf directive won't work

[stancld]

@Borda Is there any help needed to finish v0.7? :]

[Borda]

@Borda Is there any help needed to finish v0.7? :]

It would be nice, but not rush with this one =)