Fix no allowed origin

[c2tarun]

Issue #, if available:

Description of changes:
If a template with empty AllowOrigins is passed to SAM we detect and throw ValueError, this error is then left uncaught and causes service error. This PR Is converting that ValueError to a SAM specific error which is then handled properly and proper error message is returned as part of transform failure.

Description of how you validated changes:
Added functional test.

Checklist:

• Add/update tests using:
  • Correct values (already exist)
  • Bad/wrong values (None, empty, wrong type, length, etc.)
  • Intrinsic Functions
• make pr passes
• Update documentation
• Verify transformed template deploys and application functions as expected

Examples?

Please reach out in the comments, if you want to add an example. Examples will be
added to sam init through https://github.com/awslabs/aws-sam-cli-app-templates/

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

Merging #2180 (438cd85) into develop (e7a1496) will increase coverage by 0.81%.
The diff coverage is 97.38%.

@@             Coverage Diff             @@
##           develop    #2180      +/-   ##
===========================================
+ Coverage    93.58%   94.40%   +0.81%     
===========================================
  Files           90       95       +5     
  Lines         6124     6501     +377     
  Branches      1260     1307      +47     
===========================================
+ Hits          5731     6137     +406     
+ Misses         183      168      -15     
+ Partials       210      196      -14     

Impacted Files	Coverage Δ
samtranslator/model/lambda_.py	93.10% <ø> (ø)
samtranslator/plugins/globals/globals.py	99.05% <ø> (ø)
samtranslator/translator/logical_id_generator.py	100.00% <ø> (+9.09%)	⬆️
samtranslator/region_configuration.py	77.77% <63.63%> (-22.23%)	⬇️
samtranslator/model/eventsources/pull.py	90.04% <87.50%> (+11.36%)	⬆️
samtranslator/translator/translator.py	97.26% <90.00%> (+0.07%)	⬆️
samtranslator/swagger/swagger.py	94.00% <90.62%> (+0.63%)	⬆️
samtranslator/__init__.py	100.00% <100.00%> (ø)
samtranslator/feature_toggle/dialup.py	100.00% <100.00%> (ø)
samtranslator/feature_toggle/feature_toggle.py	100.00% <100.00%> (+12.16%)	⬆️
... and 27 more

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[jfuss]

LGTM