[NEOS-1085] Consolidate TransformerSource GenerateString and GenerateRandomString

[nickzelei]

  TRANSFORMER_SOURCE_GENERATE_STRING = 24;
  TRANSFORMER_SOURCE_GENERATE_RANDOM_STRING = 25;

We should deprecate one of these. I think the worker is now using GENERATE_RANDOM_STRING, but the config is named GenerateString, so a little inconsistent.

Regardless, we should pick one and mark the other for deprecation.

_{From SyncLinear.com | NEOS-1085}