fix(aws-middleware-test): add tsconfig files from aws-client-api-test

[trivikr]

Issue

Internal JS-4460

Description

The internal builds started failing since the #4850 was merged with Error:

[Error: ENOENT: no such file or directory, open 'private/aws-middleware-test/tsconfig.types.json'] {
  errno: -2,
  code: 'ENOENT',
  syscall: 'open',
  path: 'private/aws-middleware-test/tsconfig.types.json'
}

This PR just adds default TSConfig files, copied from aws-client-api-test

Testing

N/A

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[trivikr]

Created a feature request for skipping downleveling of packages under private folder at #4912

[github-actions]

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