Description: This PR aims to mergeDbConnectionInternal from the netfx and netcore projects. The strategy for this merge is to move the netfx version of the class over (since it has the entire class in one file) and do a two-step merge of the two netcore files. Once combined, the bulk of the code has no differences between the netfx and netcore implementations. The only major difference is that netfx has a collection of performance counters that are updated in certain scenarios.

The commits are broken up into fairly digestible chunks that explain each step along the process. I'd recommend reviewing the PR by stepping through the commits and seeing if you agree with the changes. This version of the PR only contains the merge, no cleanup changes were made.

Testing: Most of the functional tests run locally, though I'm having some difficulty with getting all tests to work. These issues happen main branch as well, so I assume it is unrelated to the code changes.