[ros-dev] RosTests/RosApps in GitHub CI

[Thomas Faber]

IIUC we currently always build rostests, but never rosapps in CI.
Would it be possible to analyze the changed paths instead and
* enable rostests iff modules/rostests/ or sdk/ was changed
* enable rosapps iff modules/rosapps/ or sdk/ was changed?

That should speed up builds that don't change rostests, while also
making sure that changes to rosapps aren't let into master if they break
build.

If this is nontrivial I may have a look at it myself but someone would
need to point me to the right configuration/scripts please.

Thanks!
-Thomas