Update variable replacement during deserialization to use replacement settings class and add AKV replacement logic.

[aaronburtle]

Why make this change?

Adds AKV variable replacement and expands our design for doing variable replacements to be more extensible when new variable replacement logic is added.

Closes #2708
Closes #2748
Related to #2863

What is this change?

Change the way that variable replacement is handled to instead of simply using a bool to indicate that we want env variable replacement, we add a class which holds all of the replacement settings. This will hold whether or not we will do replacement for each kind of variable that we will handle replacement for during deserialization. We also include the replacement failure mode, and put the logic for handling the replacements into a strategy dictionary which pairs the replacement variable type with the strategy for doing that replacement.

Because Azure Key Vault secret replacement requires having the retry and connection settings in order to do the AKV replacement, we must do a first pass where we only do non-AKV replacement and get the required settings so that if AKV replacement is used we have the required settings to do that replacement.

We also have to keep in mind that the legacy of the Configuration Controller will ignore all variable replacement, so we construct the replacement settings for this code path to not use any variable replacement at all.

How was this tested?

We have updated the logic for the tests to use the new system, however manual testing using an actual AKV is still required.

Sample Request(s)

• Example REST and/or GraphQL request to demonstrate modifications
• Example of CLI usage to demonstrate modifications