The basics

• I validated my changes

The details

Resolves

Fixes RaspberryPiFoundation/blockly-samples#2587

Proposed Changes

This PR updates field registration to not throw if a field is registered twice. This behavior is optional on the main registry, but is not exposed on the field registry. I considered making it optional here as well and propagating that value through, but I can't think of a reasonable case where, when you register a field, you want it to throw. I assume this was done to warn in case of accidental conflicts, but throwing seems aggressive for that vs a console.log(), and in the case of fields in particular where e.g. a field might be subclassed with the subclasses distributed as packages with no knowledge of each other, the registration code may not even be aware that it would need to allow re-registration.