This is a pretty big PR which makes our type handler binding lazy; it both helps perf in various ways (no need to set up all those exotic type handlers for everyone, and take up memory), and gets some AOT-unfriendly code out of the way unless it's really used (e.g. range binding).

This also changes how mappings are tracked across the global and connector type mappers. The global type mapper now maintains immutable mapping data structures which are simply referenced directly by the connector type mappers. If users do any mapping changes on a connector (rare), we copy-on-write the structures to the connector type mapper.

Since this is a big change, I expect there to be a bug-tail in 6.0.0 for some more exotic mapping changes. Careful reviewing would be greatly appreciated! /cc @vonzshik @NinoFloris @Brar

Closes #3816
Closes #2263
Part of #3300