Introduce schemas for map key constraints

[frenchy64]

This PR adds some schemas to help constrain the keysets of :map schemas. Instead of [:and [:map ..] [:fn <OPAQUE>]], you now write [:and [:map ...] [:xor ..] [:iff ..] ...].

The next step is to improve the generators for these schemas. The basic strategy to generate [:and S T] will be to generate S but propagate T as a hint to the S generator. Most of the work will be to canonicalize T by expanding into disjunctive normal form.

Humanization comes with the usual caveats of not being able to represent the difference between a conjunction or disjunction of errors, so some of the humanizers are a little strange. I'm not sure if this can be fixed without a breaking change to the humanization representation.

There are more general abstractions here (like the idea of simplifying a schema) but we can build towards that later. I have sketches of using such abstractions to compile optimal validators and generators. For now, concentrating on map keyset constraints is helping move this work along.

Note: the :max-tries change is to fix an unrelated flaky test:

ERROR in malli.generator-test/min-max-test (core.cljc:179)
valid properties
Exception: clojure.lang.ExceptionInfo: :malli.generator/distinct-generator-failure
{:type :malli.generator/distinct-generator-failure, :message :malli.generator/distinct-generator-failure, :data {:gen #clojure.test.check.generators.Generator{:gen #object[clojure.test.check.generators$such_that$fn__2964 0x66099385 "clojure.test.check.generators$such_that$fn__2964@66099385"]}, :max-tries 10, :num-elements [15](https://github.com/frenchy64/malli/actions/runs/12751433381/job/35538498628#step:6:16), :schema [:set {:gen/min 10, :max 20} int?]}}