fix(toolkit-lib): stack definitions for refactor are not considering resource refrences

[otaviomacedo]

The createStackRefactor method, from the CloudFormation API, requires the client to pass not only the mappings, but also the templates in the state they are supposed to be after the refactor.

Previously, this was done by iterating over the mappings (either computed by the toolkit or prescribed by the user), and using them as a list of instructions on how to modify the deployed stacks, moving resources around as necessary. This is a simple way to put the resources in their correct locations. But it becomes unwieldy when it comes to updating references between resources. Every time a resource is moved, all references to it -- and sometimes from it -- have to be updated as well.

This PR changes implements a different algorithm: take all the synthesized templates as a starting point, and adjust them so that the final templates are equal to the deployed ones up to logical IDs and references. The result is what will be sent to CloudFormation. Specifically this involves:

• Removing resources that exist locally but not remotely.
• Adding resources that exist remotely but not locally.
• Update the CDK construct path to the deployed value. (we will drop this once CloudFormation starts allowing changes in the construct path along with refactors).

One case that is not yet covered is when physical IDs are set. Because we use the physical ID plus the type of the resource to identify it, users are free to change other properties, and we can still recognize that it's the same resource. Since we are simply taking the local resource as the basis and not updating anything other than the construct path, it's possible that it differs from the deployed one. This case will be handled in a following PR.

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By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 79.21%. Comparing base (de608f6) to head (21b3b82).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #547      +/-   ##
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+ Coverage   79.09%   79.21%   +0.12%     
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  Files          47       47              
  Lines        7074     7074              
  Branches      790      796       +6     
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+ Hits         5595     5604       +9     
+ Misses       1460     1451       -9     
  Partials       19       19              

Flag	Coverage Δ
suite.unit	79.21% <ø> (+0.12%)	⬆️

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