fix: --s3-bucket or --image-repository requirement

[sriram-mv]

Which issue(s) does this change fix?

#2450

Why is this change necessary?

• only make --s3-bucket or --image-repository mandatory if there are
  resources present in the template that have locations that need to be
  packaged to different AWS destinations such as S3 or ECR.

How does it address the issue?

• look for specific packageable resource locations based on their types to determine if --s3-bucket or --image-repository is required.

What side effects does this change have?

• for templates that have zero dependence on S3 or ECR, sam package will no longer require either --s3-bucket or --image-repository

template.yaml

AWSTemplateFormatVersion: '2010-09-09'
Transform: AWS::Serverless-2016-10-31
Description: >
  python3.8

  Sample SAM Template for image

# More info about Globals: https://github.com/awslabs/serverless-application-model/blob/master/docs/globals.rst
Globals:
  Function:
    Timeout: 3

Resources:
  RailsHttpApi:
    Type: AWS::Serverless::HttpApi
    Properties:
      StageName: PROD

 ~/..../ sam package                                                                                                                                                 
AWSTemplateFormatVersion: '2010-09-09'
Transform: AWS::Serverless-2016-10-31
Description: 'python3.8

  Sample SAM Template for image

  '
Globals:
  Function:
    Timeout: 3
Resources:
  RailsHttpApi:
    Type: AWS::Serverless::HttpApi
    Properties:
      StageName: PROD

Checklist

• Add input/output type hints to new functions/methods
• Write design document (Do I need to write a design document?)
• Write unit tests
• Write/update functional tests
• Write/update integration tests
• make pr passes
• make update-reproducible-reqs if dependencies were changed
• Write documentation

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

[hawflau]

LGTM!

[jfuss]

Are there any integ tests we should add to guard against any future regressions?

[sriram-mv]

@jfuss Sure, lets add one. will be out in the next commit.