[NS 6] Migrations: handle mounted submodule tables, views, and indexes

[aasoni]

Description of Changes

Handle module migrations for modules that have mounted sub-modules. This required major surgery on the the migration step types which used "Identifier" which doesn't allow for dots or slashes.
It also required significant changes in the code that gathers and compares changes between the old and new module to correctly compare namespaced types with the corresponding mounted types.

API and ABI breaking changes

No

Expected complexity level and risk

4 - Significant change to migration code and logic. This shouldn't effect any logic for migrations that affect modules that don't have mounts, but the change is extensive enough that I think 4 is warrented.

Testing

Beyond the rust tests in the codebase that test various auto-migration cases for mounted modules I also did the following tests on sample module that had a mounted sub-module library:

• Module migrates without issue from having a submodule to not having a submodule
• Module migrates without issue from not having a submodule to having a submodule
• Module migrates without issue when having a submodule and root module change occurs (change reducer signature, add table, add column with default, change reducer function body, change index)
• Module migrates without issue when having a submodule and a submodule change occurs (change reducer signature, add table, add column with default, change reducer function body, change index)