modify @using to better support loading of submodules #1017

Job	Run time
build	1m 54s
Julia 1.6 - ubuntu-latest - x64	4m 8s
Julia 1.6 - macOS-latest - x64	4m 45s
Julia 1.6 - windows-latest - x64	14m 23s
Julia 1 - ubuntu-latest - x64	3m 36s
Julia 1 - macOS-latest - x64	4m 54s
Julia 1 - windows-latest - x64	4m 40s
Julia nightly - ubuntu-latest - x64	5m 17s
Julia nightly - macOS-latest - x64	5m 35s
Julia nightly - windows-latest - x64	6m 14s
	55m 26s

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