Fix video test

[alessandrofelder]

⚠️ Depends on #277 being merged first

Description

What is this PR

• Bug fix
• Addition of a new feature
• Other

Why is this PR needed?
The local video tests fail because we don't install, or document anywhere explicit, (AFAICT) that ffmpeg is needed (the command line tool).

What does this PR do?
Makes the video tests not local, and sets up ffmpeg on CI.

References

People have struggled with this before: #202

How has this PR been tested?

This PR adds extra tests (previously only run locally) to the CI

Is this a breaking change?

No

Does this PR require an update to the documentation?

No

Checklist:

• The code has been tested locally
• Tests have been added to cover all new functionality (unit & integration)
• The documentation has been updated to reflect any changes
• The code has been formatted with pre-commit

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (02b7565) 72.44% compared to head (f5a2de0) 81.15%.

Additional details and impacted files

@@             Coverage Diff              @@
##           mega-fix     #276      +/-   ##
============================================
+ Coverage     72.44%   81.15%   +8.71%     
============================================
  Files            26       26              
  Lines          1194     1194              
============================================
+ Hits            865      969     +104     
+ Misses          329      225     -104     

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[IgorTatarnikov]

👍 Looks good!

[alessandrofelder]

I'll try to rebase and then merge