[Tech Debt] Create connections subpackage

[mikealfare]

Problem

The connections module has outgrown its container. There are many things in this module, and it makes it difficult to troubleshoot issues. Scope of impact for methods is not clear. As a result, we have created more connections-related functionality, but spread out across other modules and even subpackages. This led to things like multiple retry methods and treating python models and sql models as completely independent workflows.

Solution

"Upgrade" the connections.py module to a connections subpackage and pull in other connections-related files to properly identify these features as connections features. This will allow us to much better encapsulate each feature and remove redundancy, thereby improving troubleshooting and ultimately decreasing bugs.

This PR serves as the first iteration in that goal. The changes in this PR are largely structural and syntactic in nature:

• move several files into /connections/ and mark them all as private
• create /connections/__init__.py and raise all members that are used outside of /connections/
• fix all imports to make it easier to see the "level" of each module relative to others
• in some cases, remove things that are not called anywhere

Checklist

• I have read the contributing guide and understand what's expected of me
• I have run this code in development and it appears to resolve the stated issue
• This PR includes tests, or tests are not required/relevant for this PR
• This PR has no interface changes (e.g. macros, cli, logs, json artifacts, config files, adapter interface, etc) or this PR has already received feedback and approval from Product or DX

[github-actions]

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