Rename environments to namespaces in the service catalog domain in ui-api-layer

[piotrmsc]

As a part of renaming environments to namespaces, we have to update namespaces in service-catalog domain in ui-api-layer as well.
Take a look at https://github.com/kyma-project/kyma/tree/master/components/ui-api-layer/internal/domain/servicecatalog there are references to environments for example in service class getter. Event activation as well (https://github.com/kyma-project/kyma/blob/master/components/ui-api-layer/internal/domain/application/eventactivation_resolver.go)

Tests if necessary should be updated as well. We have to keep in sync with console ui.
Documentation should be updated as well.

AC:

• check other places, like ApplicationMapping etc
• included: Remove deprecated usageKindResources query from ui-api #1097