Remove CombinedServices feature gate

[czeslavo]

Is there an existing issue for this?

• I have searched the existing issues

Problem Statement

We'd like to make CombinedServices feature gate a default behavior from KIC 3.0.

Proposed Solution

• Remove the feature gate
• Leave the behavior as it was turned on

Additional information

No response

Acceptance Criteria

• CombinedServices behavior is always turned on with no possibility to opt-out

[programmer04]

Possible related issues

• Remove non-combined route generation #3131
  Should be worth improving
• ingressV1ToKongServiceLegacy() using %d%d for route names which might cause 2 different routes indistinguishable #3942