Support protected registry when loading WASM image

[maleck13]

Describe the bug
When loading the WASM image we provide the registry URL to Isito via the WASMPlugin resource. However we do not have a way to configure a imagePullSecret to authenitcate against a registry that is protected.

To Reproduce

• Delete any existing policies
• Set the RELATED_IMAGE_WASMSHIM in the operator subscription to one behind a protected registry
• Create a new policy
• Watch the logs of Istio it will fail to load the image as it is unauthenticated.

Expected behavior

• Provide a way to accept a imagePullSecret that we could then pass on to the WASMPlugin resource created in response to a policy being created.

Additional context
Manual Workaround.

[maleck13]

One option here would be to allow users to specify an imagePullSecret in the kuadrant-operator via the kuadrant resource or some other mechanism such as an EnvVar, we would then expect that secret to be in the same namespace as the gateway. If it is not there it is an error and the WASMPlugin is not setup cc @eguzki

[eguzki]

For the context, some PoC's done in the past:

• Kuadrant dedicated service to serve wasm binary via HTTP kuadrant wasm server component #593
• Wasm binary served from kuadrant operator workload Wasm binary served from kuadrant operator workload  #686