feat: support RouteSettings for HttpApi

[keetonian]

Issue #, if available:
#1451

Description of changes:
Support RouteSettings at multiple levels.

Description of how you validated changes:
Deployed templates to verify changes.

Checklist:

• Write/update tests
• make pr passes
• Update documentation
• Verify transformed template deploys and application functions as expected
• Add/update example to examples/2016-10-31

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

[praneetap]

Also add it to globals documentation.

[codecov-io]

Codecov Report

Merging #1490 into develop will increase coverage by 0.03%.
The diff coverage is 100%.

@@             Coverage Diff             @@
##           develop    #1490      +/-   ##
===========================================
+ Coverage     94.1%   94.13%   +0.03%     
===========================================
  Files           78       78              
  Lines         4900     4926      +26     
  Branches       988      991       +3     
===========================================
+ Hits          4611     4637      +26     
  Misses         134      134              
  Partials       155      155

Impacted Files	Coverage Δ
samtranslator/model/eventsources/push.py	90.78% <ø> (ø)	⬆️
samtranslator/plugins/globals/globals.py	99.05% <ø> (ø)	⬆️
samtranslator/model/sam_resources.py	94.29% <ø> (ø)	⬆️
samtranslator/model/apigatewayv2.py	94.73% <ø> (ø)	⬆️
samtranslator/plugins/api/implicit_api_plugin.py	98.24% <100%> (+0.01%)	⬆️
...translator/plugins/api/implicit_http_api_plugin.py	97.43% <100%> (+0.94%)	⬆️
...translator/plugins/api/implicit_rest_api_plugin.py	100% <100%> (ø)	⬆️
samtranslator/model/api/http_api_generator.py	92.27% <100%> (+0.06%)	⬆️

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