Allow creating Actions in other namespaces than `default`

[pkosiec]

Description

• Add dropdown to choose a namespace
• Maybe it should be a global dropdown, in the top-right sight of the UI? Similarly to AWS regions
• Support namespaces in both Action creation wizard and Action management view

This task is related to capactio/capact#508, as the namespaces will presumably go away once User authentication is in place. Or, maybe user will be able to use different namespaces as well - if so, this task is still valid.

Reason

This is a missing feature, comparing to the Capact CLI and GraphQL API.

Use cases

As System User, I want to manage Actions in different Kubernetes namespaces.