fix: pack throws getting api-mesh

[MichaelGoberling]

Description

Start using the --json flag when getting api-mesh during aio app pack and throw any resulting stderr

Related Issue

Closes #773

Motivation and Context

How Has This Been Tested?

Locally linked plugin, npm run test

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• I have signed the Adobe Open Source CLA.
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (73a01b2) 100.00% compared to head (ce0e98d) 100.00%.

Additional details and impacted files

@@            Coverage Diff            @@
##            master      #774   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           56        56           
  Lines         3231      3232    +1     
  Branches       613       614    +1     
=========================================
+ Hits          3231      3232    +1     

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[shazron]

Forgot to update this with --json, was waiting for the PR to be approved and forgot about it. Thanks Michael! adobe/aio-cli-plugin-api-mesh#61