[HttpKernel] changed the fragment handler to explicitely disallow non-scalar in generated URIs (refs #8263)

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #8263
| License       | MIT
| Doc PR        | n/a

When using the `render()` function in Twig with a `controller()` reference, the attributes can contain non-scalar. That's fine for the inline strategy, but it cannot work for other strategies as it then involves a proper HTTP request.

So, this PR properly throw an exception in such situations to avoid difficult to find bugs.