dev-docs: refactor and add information for newbies (#1912)

* refactor dev-docs structure and add information

* improve doc

* Update dev-docs/workflows/create-debug-cluster.md

Co-authored-by: Daniel Weiße <66256922+daniel-weisse@users.noreply.github.com>

* Update dev-docs/workflows/create-debug-cluster.md

Co-authored-by: Daniel Weiße <66256922+daniel-weisse@users.noreply.github.com>

* pr feedback daniel

* Update dev-docs/README.md

Co-authored-by: Daniel Weiße <66256922+daniel-weisse@users.noreply.github.com>

* move to howto again

* split up dev-setup and pull-request into sep files

* fix backticks

* add writing style convention + testing repo

* remove OSS cluster + reduce plugins vs code

* update bazel pre-pr doc

* ghcr img private hint

* add fetch measurement + provider sub-directory hint

* add label doc + pr title check in template

* add OSS build comment

* Update CONTRIBUTING.md

Co-authored-by: Thomas Tendyck <51411342+thomasten@users.noreply.github.com>

* Update CONTRIBUTING.md

Co-authored-by: Thomas Tendyck <51411342+thomasten@users.noreply.github.com>

* Update dev-docs/README.md

Co-authored-by: Thomas Tendyck <51411342+thomasten@users.noreply.github.com>

* Update dev-docs/workflows/dev-setup.md

Co-authored-by: Thomas Tendyck <51411342+thomasten@users.noreply.github.com>

* thomas feedback

* add go proverb mention

---------

Co-authored-by: Daniel Weiße <66256922+daniel-weisse@users.noreply.github.com>
Co-authored-by: Thomas Tendyck <51411342+thomasten@users.noreply.github.com>

dev-docs/howto/longhorn.md

@@ -52,4 +52,4 @@ index 00000000..355a2f83
 +
 +[Install]
 +WantedBy=multi-user.target
-```
+```