Add new assertions to some of the ALC tests to ensure no assembly duplication #42468
Description
As part of #42425 a new test was added to specifically catch the customer scenarios where we regressed, but we need to look and see why this wasn't caught by the existing ALC tests and update the assertions accordingly. A lot of tests were passing by just naively loading all requested assemblies into the active ALC, which means we aren't checking to make sure assemblies aren't being duplicated inappropriately.
It's possible this was covered in the DefaultContext test, which is extremely large/complicated and broken on wasm for other reasons related to the VFS, but I don't think so. We should add assertions to some of the existing tests to ensure this extremely naive loader behavior does not just pass most of our test suite without issue.