Disable the ability to use Istio WASM filters

Istio upstream builds WASM extensions for telemetry but don't use them by default, for performance reasons.

For instance, see https://github.com/istio/istio/blob/release-1.9/manifests/charts/istio-control/istio-discovery/templates/telemetryv2_1.9.yaml#L41

and https://github.com/istio/istio/blob/release-1.9/manifests/charts/istio-control/istio-discovery/values.yaml#L144

We were doing the same.

Because of issues building these WASM extension filters in brew, we are going to ship proxy without .wasm extensions. Thus we should patch those charts removing the conditional and hard coding the usage of the null runtime (compiled-in filter).

This effectively means the usage of the Values.telemetry.v2.*.wasmEnabled fields will be ignored. I'm not sure how this is handled in SMCP v2, I guess it is via techPreview? If so, we don't need to do anything in the operator, correct?

We can apply these changes directly in maistra/istio repository, likely in the 2.1-1.9 branch, because it affects 1.9 charts as well.

We should also document this as a difference to upstream (although a minor one, since they are not used by default).

Usage of .wasm files from upstream is an alternative. They should work as they are bytecode anyway. Not sure if we are allowed to ship/use/recommend them, because they are binaries not built by us.