Replace Managed Policy with equivalent inline policy

[ConnorKirk]

Some scanners are triggered by the presence of the AmazonAPIGatewayInvokeFullAccessmanaged policy. This commit replaces the managed policy with an equivalent inline policy that will not trigger scanners. There's a small security win in being able to scope the API Gateway resource to the specific Account and Region.

Issue #, if available:

Description of changes:

PR Checklist:

• Changelog updated
• Unit tests (and integration tests if applicable) provided
• All tests pass
• Pre-commit checks pass
• Debugging code removed
• If releasing a new version, have you bumped the version in the main CFN template?

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 99.71%. Comparing base (cb48fca) to head (2c596e2).

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #405   +/-   ##
=======================================
  Coverage   99.71%   99.71%           
=======================================
  Files          31       31           
  Lines        1742     1742           
=======================================
  Hits         1737     1737           
  Misses          5        5           

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