Add core/secret-set and core/secret-get

[sebastianrath]

This PR introduces a new node called core/secret-set and renames the old core/secret node to core/secret-get for consistency. I also fixed a few bugs in the e2e tests and reference files that slipped in. I also fixed an issue where visited data nodes were not properly traversed during the exception print.

Error fix:

error:
   1: execute 'Start' (start)
   2: execute 'Print' (print-v1-panda-orange-peacock)
   3: request input from 'Run Executable' (run-exec-v1-wolf-guava-gray)
      error when requesting input from [...] **first** input port 👈 This info was missing
       ↳ output port 'output' has no value