[print] Simplify custom print-method detection#419
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Drop the per-class cache (deftype + ConcurrentHashMap + generation tracking) in favor of comparing the live get-method result against the generic collection registrations - MultiFn's own dispatch cache does the heavy lifting, and staleness handling disappears because every lookup sees the current registrations. Add *honor-print-method* so consumers can turn the whole feature off per context.
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Following up on the concern that #415 brought too much complexity: this strips the mechanism down to its minimum while keeping the behavior.
custom-print-method?now compares the liveget-methodresult against the generic collection registrations;MultiFn's own dispatch cache does the heavy lifting, and all the staleness/invalidation logic disappears because every lookup sees the current registrations.*honor-print-method*dynamic var (default true) gates the feature, making it a per-context decision - the inspector, the debugger or cider-nrepl can bind it off wherever structural output is preferable.Numbers on a collection-heavy benchmark (100 prints of ~4000 nested values): master baseline ~80ms, the cached version ~87ms, this version ~102ms. With the var bound to false there's no overhead at all. I don't think the difference matters for a tooling printer, but if it does, flipping the default to false makes the feature free and purely opt-in - that's a policy call I'm leaving open here.
Net effect: about 50 lines less, no deftype, no atom, no concurrency reasoning.
cc @alexander-yakushev