reduce places where Builtins are listed (#58205)
DRY code somewhat by consolidating builtin declarations to use a table
or macro definition to auto-generate the required reflection metadata.
Mostly NFC, but does include a couple bugfixes caused by the consistency
this enforces. Adding a new `Builtin` is now simply a matter of
declaring it in `builtin_proto.h` and defining it in `builtins.c` and
any relevant declarations are handled automatically.
