[DO NOT MERGE] TLA+ type annotations

[lemmy]

...for posterity.

Additional pointers/background material:

TLA+ type annotations

• https://apalache.informal.systems/docs/adr/002adr-types.html#11-type-grammar-type-system-1-or-ts1
• https://apalache.informal.systems/docs/lang/variants.html
• https://github.com/informalsystems/apalache/blob/main/tlair/src/main/scala/at/forsyte/apalache/tla/types/parser/tokens.scala
• https://github.com/microsoft/tlaplus-examples/tree/gptools/genaisrc

3DGen/Everparse

• https://github.com/project-everest/everparse/blob/master/src/3d/ocaml/parser.mly
• https://github.com/project-everest/everparse/issues/57