Improve dispatch in code loading

CodeTracking.jl (a foundation for Revise & JuliaInterpreter)
defines additional `PkgId` methods; leaving this
untyped leads to invalidation of the entire code-loading path.

Author: timholy

base/loading.jl

@@ -715,6 +715,7 @@ function _tryrequire_from_serialized(modkey::PkgId, build_id::UInt64, modpath::U
                 invokelatest(callback, modkey)
             end
             for M in mod::Vector{Any}
+                M = M::Module
                 if PkgId(M) == modkey && module_build_id(M) === build_id
                     return M
                 end