Renamed submodules does not play well with precompilation

[fredrikekre]

This package code:

module ForgetImports

    import Pkg.PlatformEngines as pe
    import Pkg as p

    function test()
        println("Pkg = ", p)
    end

    function test2()
        println("PlatformEngines = ", pe)
    end

end # module

results in the following error if the module is precompiled

$ julia -q
julia> using ForgetImports

julia> ForgetImports.test()
Pkg = Pkg

julia> ForgetImports.test2()
ERROR: UndefVarError: pe not defined
Stacktrace:
 [1] test2()
   @ ForgetImports /tmp/tmp.wXr6KYv8f2/ForgetImports/src/ForgetImports.jl:11
 [2] top-level scope
   @ REPL[3]:1

Works fine without precompilation:

$ julia --compiled-modules=no -q                           
julia> using ForgetImports

julia> ForgetImports.test()
Pkg = Pkg

julia> ForgetImports.test2()
PlatformEngines = Pkg.PlatformEngines

(Tentatively putting on 1.6 milestone since the rename feature is new for 1.6).