Add --no-tests flag to nf-core modules install

[edmundmiller]

The discussion we had at the hackathon was that by default the tests should be installed, and users should have to opt-out of the bad practice of not testing.

However, I think instead it might be simpler for everyone to not install the tests, unless the user runs nf-core modules patch and then the tests get installed. The tests would get removed when they remove the patch.

[maxulysse]

I would love sooo much to have that

[edmundmiller]

https://nfcore.slack.com/archives/CE5LG7WMB/p1744885635236059

[mashehu]

After a discussion inside @nf-core/infrastructure, we agree that we should by default not add modules/subworkflow tests inside pipelines, but provide a flag to still install them (and if people create a patch, we ask if they want to fetch the tests as well)