Default global operator to `camel` namespace

### Requirement

As we're doing also for Camel Monitor Operator [1], it is convenient to move the default to `camel` namespace so that all Camel based operators are deployed by default in the same namespace.

[1] https://github.com/camel-tooling/camel-monitor-operator/pull/195

The issue names no file or test; start by locating the global operator's default namespace in the camel-k repository and compare the referenced Camel Monitor Operator change. Verify that a fresh global operator deployment defaults to the camel namespace, then run the relevant existing tests.

Written by the indexing model from the issue text.