Go 1.21 renamed runtime._type to internal/abi.Type and changed the name
of its fields. Update Delve so that it uses the new names for loading
interfaces and generic type parameters.
Go 1.20 switched to uint64 to represent goroutine IDs, we can't
actually follow suit because we have allowed clients to use -1 to refer
to the currently selected goroutine, however we should at least switch
to int64 and also update the rtype check to accept the 1.20 type.
Adds a script that check automatically that the the assumptions that
pkg/proc makes about runtime are met by the actual runtime, using a
combination of parsing and magic comments.
Also emits a file describing all the struct fields, constants and
variables of the runtime that we use in pkg/proc.
