fix: ACNA-1814 - aio app init --standalone-app should not ask for overwrite input

[shazron]

This is based on the master branch code, tested via the @adobe/aio-cli-next CLI.

Closes #581

How Has This Been Tested?

• npm test
• manual test

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

Merging #585 (50b8973) into master (fc3b1c0) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##            master      #585   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           53        53           
  Lines         2804      2804           
  Branches       528       528           
=========================================
  Hits          2804      2804           

Impacted Files	Coverage Δ
src/commands/app/init.js	100.00% <ø> (ø)

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