Eliminate glimmer-engine dependency duplication.

[dgeb]

Currently, glimmer-build requires that tests be run with an AMD loader. This approach was taken for expediency and has not been re-examined since these libs were created.

Originally, glimmer-di just had a dependency on glimmer-engine, which includes an AMD distribution. The glimmer-util package was created later and should supersede glimmer-engine, but glimmer-util does not include an AMD distribution. So glimmer-di maintains its glimmer-engine dev dependency only for testing. It's clear that this dependency duplication needs to be eliminated.

If we want to continue to run tests with AMD modules, glimmer-build could be tweaked to compile AMD from glimmer-util's source modules OR glimmer-util could simply export AMD with its distribution. Or perhaps we should re-examine the AMD testing approach altogether.