apiviewgo considers cross-module alias versions within SDK

For example, `azcore` exports types defined in `internal`. Today, when parsing `azcore`, apiviewgo parses the source code of `internal` it finds on disk next to `azcore`. This is incorrect because it ignores the `internal` version `azcore` requires--apiviewgo just parses whatever code is on the checked-out branch and can include irrelevant, pre-release `internal` API in `azcore` reviews. apiviewgo should instead parse the `internal` version specified in `azcore/go.mod`.

Start by tracing how apiviewgo resolves the `internal` source while parsing `azcore`, then inspect `azcore/go.mod` and compare that required version with the checked-out code. Done means reviews parse the `internal` version specified by `azcore/go.mod` rather than an unrelated or pre-release version found next to it.

Written by the indexing model from the issue text.