Respect cluster-wide proxy settings in Camel K

This comes from Knative.

Desc:

In the corporate case, the OpenShift cluster is not connected to the internet by default, but there's a proxy that gives access to whitelisted places.
A proxy config in OpenShift is created and all the things running on OpenShift should respect the proxy information and use it.

None of the the operator nor the the source/channel controller need to go and read the proxy config directly; it is passed by OLM.

OLM passes the proxy information to the operators using HTTP_PROXY, HTTPS_PROXY and NO_PROXY env vars to the operators.
Operators then need to read this env vars and also propogate them to the controllers they create.
Similarly, custom TLS cert bundles should be supported. An example is here: https://issues.redhat.com/browse/SRVKS-444

By default, Golang should pick up the HTTP_PROXY, HTTPS_PROXY and NO_PROXY env vars and use them.
That means,
1. Operator should read the env vars, propogate them to CamelSource controller
2. CamelSource controller should read the env vars, propogate them to CamelSource containers
3. CamelSource containers should do the same for the containers they create (like receive adapter containers, Camel builds containers, Camel integration containers, etc.)

Example PR for Knative Serving: https://github.com/openshift-knative/serverless-operator/pull/122 to support HTTP and HTTPS_PROXY.

Some notes:

• How to setup proxy server: mitm proxy Privoxy -1 Privoxy -2
• How to configure proxy settings on OpenShift: 1 2

More info and history: SRVKE-227