Base: avoid losing Method provenance in `@enum` (#61932)

Improves stacktraces and `methods(...)` queries for any Methods defined
through @enum:

```julia
julia> @enum Fruit Apple=1 Banana=2
julia> methods(Fruit)
 [1] Fruit(x::Integer)
     @ REPL[6]:1
```

versus before:
```julia
julia> methods(Fruit)
 [1] Fruit(x::Integer)
     @ Enums.jl:211
```