matching: use polymorphic variants to classify general/half_simple/simple patterns (#9361)
matching: use polymorphic variants to classify general/half_simple/simple patterns (#9361)

Also: these types are now instances of Typedtree.pattern_data.

Co-authored-by: Gabriel Scherer <1912fc14072add306a707dab97c91935b2c8582d@gmail.com>
gerdstolpmann/ocaml,gerdstolpmann/ocaml,gerdstolpmann/ocaml,gerdstolpmann/ocaml,gerdstolpmann/ocaml