feat: marker validation (marker name)

[lander2k2]

Currently, we do not handle improper markers (e.g. i specify operator-builder marker with unknown marker names). This would pass through and just work, however, will be confusing to end users. We should:

1. Error out when we find an +operator-builder marker with invalid marker definitions (e.g. field, collection:field, and resource are all valid). If someone were to type resource as rsrc, we should notify them and not build their operator.