Adding VPC Access Policy when VpcConfig is present

[eugeniosu]

Issue #, if available:
#1169

Description of changes:
The managed policy service-role/AWSLambdaVPCAccessExecutionRole is added when the property VpcConfig is present .

Description of how you validated changes:
I updated the tests to check that the generated role contains service-role/AWSLambdaVPCAccessExecutionRole

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.

[codecov-io]

Codecov Report

Merging #1228 into develop will increase coverage by <.01%.
The diff coverage is 100%.

@@             Coverage Diff             @@
##           develop    #1228      +/-   ##
===========================================
+ Coverage    94.48%   94.49%   +<.01%     
===========================================
  Files           72       72              
  Lines         3738     3740       +2     
  Branches       740      741       +1     
===========================================
+ Hits          3532     3534       +2     
  Misses         104      104              
  Partials       102      102

Impacted Files	Coverage Δ
samtranslator/model/sam_resources.py	95.65% <100%> (+0.02%)	⬆️

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[ShreyaGangishetty]

@eugeniosu Thank you contributing this!
Could you please resolve the merge conflicts and update the PR?

[ShreyaGangishetty]

I have resolved the merge conflicts.
This PR looks good to me!

[praneetap]

Thanks for your contribution!