Add generate-<statement> family of commands

Most of OAK is geared around *lookup*. There are commands to lookup

- edges
- definitions (text)
- logical definitions
- aliases
- mappings

Some of these are parameterized, For edges you can pass in `--entailed` and it will yield entailed edges (this is still technically lookup as these are calculated in advance by relation-graph)

We have an existing lexmatch command which yields results similar in structure to the mappings command, except these are generated rather than a lookup

We can also distinguish rule-based methods, fuzzier predictive methods, lexical, ...

Should we try and unify this a bit more? We could have a `generate-X` command shadow existing commands

- generate-synonyms:
- synonymizer (simpler regex based rules)
- future BERT based plugin
- generate-edges
- link prediction via oakx-grape plugin
- entailed edges? Technically these are not "predictions:
- generate-mappings
- lexical approaches (lexmatch)
- future plugins using link prediction, semsim, etc
- generate-definitions
- rule based e.g. dosdp, could be wrapped as a plugin
- future NLP generation based (plugin)

(I originally has `predict-X` but I think predict has a narrower meaning)

Another option is to fold these into the main commands, the way we do with entailments for edges. But I think this would be over-abstraction. This would explode command line options, and the data model for generated objects may different ones that are merely looked up.

cc @matentzn @caufieldjh @justaddcoffee @hrshdhgd

Start by reading the existing lexmatch command and the current lookup commands for edges, definitions, aliases, and mappings. Compare how generated results differ from looked-up results, then clarify which generate-* commands and plugins are in scope. Done means an agreed command structure and implementation plan, since this issue currently presents alternatives rather than a defined change.

Written by the indexing model from the issue text.