Support "Logical DNS" in Static Upstream

[DuncanDoyle]

Gloo Edge Product

Enterprise

Gloo Edge Version

1.16.4

Is your feature request related to a problem? Please describe.

Gloo Edge currently has basically 2 modes to define Upstreams:

Upstream Type | Envoy Cluster
Static        | STRICT_DNS
Kube          | EDS

Strict DNS has some limitations when used with large scale web-services that use a round-robin type DNS, as explained in the Envoy documentation: https://www.envoyproxy.io/docs/envoy/latest/intro/arch_overview/upstream/service_discovery#logical-dns (see the second paragraph of the "Logical DNS" section).

We currently have no options in GE to use Envoy's "Logical DNS" configuration.

Describe the solution you'd like

Add a new configuration option in Static Upstreams to allow users to configure "Logical DNS", so we would have the following support in Upstreams:

Upstream Type | Envoy Cluster
Static        | DNS (STATIC || LOGICAL)
Kube          | EDS

Describe alternatives you've considered

n.a.

Additional Context

We've seen scenario's where Static Upstreams using STRICT_DNS give issues in certain environments.