Change default namespaces + Support skipping release installation

[sbernauer]

The idea is to not implement this in the current version of stackablectl, but instead wait for the remake. This issue only tracks the requirements

As discussed on-site on 2023-05-09 we want

• A flag to skip installing the release when installing a stack or demo
  • Print a warning, that users are responsible to install operators in the correct version
• You can configure the namespace to deploy operators into
  • We default to stackable-operators
• You can configure the namespace to deploy the stack + demo into
  • We default to stackable
• stackablectl tries to create specified namespaces if not existing
  • If this fails because of missing permissions an error is thrown as the user is suggested to specify operators and demo namespace manually
• Demos have the possibility to say "i can only run in stackable-demo" namespace (in stacks.yaml or demo.yaml). If they do so, a warning is printed when they are installed in a different namespace, saying the demo will likely not work. This can be the case as we have to use FQDN service names so that the TLS certs are valid

[razvan]

Looks good to me except that it's not clear how the namespace is specified. I hope that releases will use the existing --namespace command line argument. For demos a new config field probably. Correct ?

[Techassi]

We currently consider --operator-namespace and --demo-namespace.

[sbernauer]

Saschas and my's current state of suggestion

# All args are optional
stackablectl --operator-namespace stackable-operators operator in commons
stackablectl --operator-namespace stackable-operators release in 23.7
stackablectl --operator-namespace stackable-operators --product-namespace|-n stackable stack in monitoring
stackablectl --operator-namespace stackable-operators --product-namespace|-n stackable demo in lakehouse

# Output after installing demo/stack mentions: bla installed. Used "stackable stacklet ls -n <just-used-ns>" to list the deployed stacklets

# In case no namespace is given, stacklets from *all* namespaces will be listed. --all-namespaces will be removed
stackablectl stacklet ls --product-namespace|-n stackable

@razvan would that work for you?