DefaultGetProxyValue default implementation which only pulls from the current environment variables.

GetProxyValues returns a set of environment variable for a Bash shell command.

SetGetProxyValueFunc save the function used to return a string value for a Proxy based on the string prefix passed.

SetHTTPSProxy defines the HTTPS_PROXY env var value for all the cmd executions.

SetPreProxyFunc save the function used to run before processing proxies This is currently used by Gnome UI to copy Network Proxy from install user.

GetProxyValueFunc is the type of the GetProxyValue function.