refactor(cli): new internal cloudformation api module

[mrgrain]

Pulls some shared "cloudformation" helpers into a new internal api module. This resolves some annoying inter-dependencies between internal modules and specifically breaks up the deployment mega module a bit.

Also moves some other files from api/util so that it's now almost gone (which is the goal).

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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

[mrgrain]

this is a collection of helpers that were previously in api/deployments but in reality were used across multiple modules that don't have anything to do with deployments.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 92.88256% with 20 lines in your changes missing coverage. Please review.

Project coverage is 85.44%. Comparing base (0d7bcca) to head (966b224).

Files with missing lines	Patch %	Lines
...es/aws-cdk/lib/api/cloudformation/stack-helpers.ts	93.12%	13 Missing ⚠️
.../lib/api/cloudformation/template-body-parameter.ts	50.00%	6 Missing ⚠️
packages/aws-cdk/lib/api/deployments/cfn-api.ts	90.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #270      +/-   ##
==========================================
+ Coverage   85.24%   85.44%   +0.19%     
==========================================
  Files         219      221       +2     
  Lines       36499    36512      +13     
  Branches     4440     4464      +24     
==========================================
+ Hits        31115    31198      +83     
+ Misses       5287     5216      -71     
- Partials       97       98       +1     

Flag	Coverage Δ
suite.unit	85.44% <92.88%> (+0.19%)	⬆️

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