Constraint traits not rendered when applied directly on enums

[kubukoz]

$version: "2"

namespace input

@length(min: 1)
enum A {
  GOOD
}

output:

val tag: EnumTag[A] = EnumTag.ClosedStringEnum
implicit val schema: Schema[A] = enumeration(tag, values).withId(id).addHints(hints)

https://smithy4s-codegen-ui.fly.dev/index.html#code=CQNwpgTgzglg9gOwFwAIBEAmNAobCCGAtmFAA74DGYKMCpArgC64ACANmAgOaMAWAFIVqoAjAEpsneoRQBBFAG9sKFAHEA8uoAi2AL5A;dependencies=

Notably, Smithy allows it and we already support constraint traits on members that target enums (see #1283), we just skip them on the enum schema itself.