Bzlmod: Support querying/inspecting external dependencies

[Wyverald]

We should have a new subcommand in Bazel that allows the user to query/inspect external dependencies.

[andyrinne12]

I am working on developing an inspection tool for the Bzlmod external module dependency system (Manage external dependencies with Bzlmod | Bazel) (somehow similar to bazel query Bazel Query How-To).

My experience with complex dependency trees is not very vast, therefore I would really appreciate some suggestions on what problems you have encountered and what features may be interesting or useful.

Feel free to suggest improvements on the possible usages as well as on the actual syntax and output of the commands. Here you can find the Design Document.