Retrieve All Accessible Variables in a WfRun

[mijailr]

The ListVariables method currently returns only the variables owned by a WfRun and does not include those inherited from a parent WfRun.
The request is to include them in the response and still preserve the access level to diferentiate them.

Proposal

Modify the ListVariables method to also include inherited variables in the response while preserving the access level to differentiate them.

ex:

// A list of Variables.
message VariableList {
  // A list of Variable objects.
  repeated VariableListResult results = 1;
}

message VariableListResult {
  WfRunVariableAccessLevel access_level = 1;
  Variable variable = 2;
}