Add parity tests and refactor logic for CFn stack resource updates

[whummer]

Add parity tests and add a number of smaller fixes in the logic for CloudFormation stack resource updates. Addresses #6155

The main issue with the sample shared by the user is that SAM deployment was hanging, as the stack/resource status was incorrectly reported as CREATE_COMPLETE instead of UPDATE_COMPLETE. This led to the discovery of a few more issues, which are now fixed, and covered by parity tests.

Summary of changes:

• properly set the status of stack resources as CREATE_COMPLETE or UPDATE_COMPLETE, depending on the operation and prior existence of resources within the stack
• add a parity/snapshot test for the point above (which is essentially what caused SAM/samlocal to hang when deploying the sample in samlocal not returning on second and later deploys #6155)
• ensure that Parameter instances are not being returned from the list of stack resources in DescribeStackResources
• remove a few attributes in API response messages to avoid ASF response serializer warnings
• minor simplifications, e.g., removing stack_name from apply_changes(..) method
• add missing resource methods to CDK::Metadata model, returning synthetic data (surfaced as being required when testing the changes)
• fix an assertion in test_cfn_with_multiple_route_tables and parity test it against AWS - previously we were creating/asserting 3 route tables instead of 4 (validated against AWS)

Note: part of the changes in the PR is to avoid us changing the resource action (from "Modify" to "Add"), and instead introducing a "_deployed" attribute that allows us to determine whether the resource needs to be created or updated - see TODO in the code. This is only a workaround for now, and should be fixed as part of a larger refactoring after introducing model classes for the state of the resources in a stack (e.g., using a cached property). To be discussed in more detail @dominikschubert ... 👍

[github-actions]

LocalStack integration with Pro

       3 files  ±0         3 suites  ±0   1h 10m 41s ⏱️ - 8m 7s
1 240 tests +1  1 199 ✔️ +2  41 💤  - 1  0 ❌ ±0 
1 665 runs  +1  1 593 ✔️ +2  72 💤  - 1  0 ❌ ±0 

Results for commit 97a2027. ± Comparison against base commit 31286eb.

♻️ This comment has been updated with latest results.

[coveralls]

Coverage decreased (-0.02%) to 91.563% when pulling 97a2027 on cfn-parity-stack-updates into 31286eb on master.

[dominikschubert]

LGTM 👍

The workaround is fine for me for now. As you've said, this will be changed/removed at a later point anyway.

Parity 🚀 🚀