Parse, create, and print isorecursive recursion groups (#4464)

In `--hybrid` isorecursive mode, associate each defined type with a recursion
group, represented as a `(rec ...)` wrapping the type definitions in the text
format. Parse that text format, create the rec groups using a new TypeBuilder
method, and print the rec groups in the printer.

The only semantic difference rec groups currently make is that if one type in a
rec group will be included in the output, all the types in that rec group will
be included. This is because changing a rec group in any way (for example by
removing a type) changes the identity of the types in that group in the
isorecursive type system. Notably, rec groups do not yet participate in
validation, so `--hybrid` is largely equivalent to `--nominal` for now.

0 files changed, 0 insertions, 0 deletions