refactor(build): remove namespace from IT matrix and move into harness

[GeorgeMac]

Related to #3144

I am working on a series of refactors to make our ITs clearer and ultimately faster (due to less work).
The primary motivation is we intend to introduce authz test suites to the ITs in the coming week.
However, our ITs are already exploding a little too much.
So, we decided to remove some of the dimensions from the integration matrix at the Dagger level.
This is starting with namespace in this PR.
I will continue to auth next and that will be a bigger shift in how we go about testing auth.

In this PR, namespace is dropped from the test harness matrix.
Instead, namespace is now a parameter that is exercised in the harness itself.
This results in a considerably quicker suite, as we half the number of isolated entire IT suites.
The tests in the harness itself still exercises the different namespace arguments (empty, default and production).

Note: I also dropped all the edge cases for namespaced tokens.
This was deliberate as they already over complicated things and it got more confusing without the namespace scope.
Instead, this will be reinstated when with come to explicitly address authz (very shortly after I do the auth refactor).

[markphelps]

nice!