feat: add Argo CD Application

[maximilianbraun]

Description of your changes

• added support for Argo CD Applications
• added conversion of structs via goverter (used within Crossplane as well)
• added mockgen to be executed with go generate ./...
• added 2 make targets for simpler local dev + little shell script
• updated k8s clients, i had some issues with building
• updated golangci-lint version, which contained a contained a couple fixes regarding resource usage

I have:

• [x] Read and followed Crossplane's contribution process.
• [x] Run make reviewable test to ensure this PR is ready for review.

How has this code been tested

Unit tests have been added to the controllers & manual integration tests.

[janwillies]

Thanks a lot @maximilianbraun for this massive contribution! We'll take a look soon

[MisterMX]

Thanks for your contribution @maximilianbraun! Can you take a lot a the remarks I have added?

[maximilianbraun]

Thanks for your contribution @maximilianbraun! Can you take a lot a the remarks I have added?

Sure thing. Let me have a look :)

[maximilianbraun]

@MisterMX your comments should be addressed. I added an .editorconfig so others don't fall in the LF pitfall.

Let me know when you spot something.

[maximilianbraun]

@MisterMX done. It just came with the caveat that I had to initialise the external-name within the test, since the initialisers don't run there.