Support IPrintWithWriter (CLJS)

[borkdude]

Similar to print-method.

Some notes:

1) SCI implements protocols methods as multimethods 2) In JVM print-method is not included by default, it needs access to the host print-method multimethod 3) SCI records are based on one Clojure / CLJS record type which defers to a runtime SCI type. When implementing print-method for a SCI records, some state is mutated which affects the general Clojure / CLJS print-method for the general record type which dispatches on the SCI type. 4) To let users implement IPrintWithWriter in general (not records), we could do two things:

• Have a multi-method counterpart which defers to the protocol (this is done for e.g. IDeref in SCI). This comes with performance overhead for printing though.
• Mutate the IPrintWithWriter CLJS protocol directly (given access to the host, or, presence of this protocol in the SCI config) 5) But since SCI records all share one CLJS record type, 4 isn't sufficient, so we need to defer to some indirection anyway which can be mutated given the SCI type of the record.

Also see https://github.com/babashka/sci/issues/639

It seems, just for SCI records, we don't need to implement IPrintWithWriter for all use cases, so maybe starting with 5 and working our way back is the best approach.

[borkdude]

@grzm I pushed something to printwithwriter (not ready).

If we can get SCI to put (-pr-writer ..) functions as metadata on the record var under :sci.impl/print-method then it should work.

So we should add some hard-coded check of IPrintWithWriter implementations and then handle that separately.