refactor: plugin platform code cleanup

[jhockett]

Description of changes

Issue #, if available

Description of how you validated changes

Checklist

• PR description included
• yarn test passes

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 #10384 (3e88cf5) into master (714f2fa) will increase coverage by 0.01%.
The diff coverage is 64.86%.

@@            Coverage Diff             @@
##           master   #10384      +/-   ##
==========================================
+ Coverage   46.57%   46.59%   +0.01%     
==========================================
  Files         703      703              
  Lines       35246    35237       -9     
  Branches     7134     7133       -1     
==========================================
  Hits        16417    16417              
+ Misses      17042    17035       -7     
+ Partials     1787     1785       -2     

Impacted Files	Coverage Δ
...ify-cli/src/plugin-helpers/scan-plugin-platform.ts	21.10% <45.71%> (+3.24%)	⬆️
packages/amplify-cli/src/plugin-manager.ts	17.64% <72.00%> (+0.25%)	⬆️
...es/amplify-cli/src/plugin-helpers/verify-plugin.ts	100.00% <100.00%> (ø)
...li/src/domain/amplify-usageData/getUsageDataUrl.ts	100.00% <0.00%> (+12.50%)	⬆️

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[sachscode]

LGTM