Reimplement sqlite3.capi.sqlite3_close_v2() and sqlite3session_delete() as a hand...

Reimplement sqlite3.capi.sqlite3_close_v2() and sqlite3session_delete() as a hand-written bindings so that they can attempt to clean up certain (potentially) FuncPtrAdapter-installed functions before closing. Correct the create-function family of JS-to-function-pointer automated conversions to include the UDF's arity as part of the mapping's key so that (un)binding a UDF to different functions for different arities works (and add tests confirming it). Correct a broken doc link in module-symbols.html.

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