refactor findUploadId to TypeScript

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also refactor API to use async/await

testing script:

import * as minio from 'minio'
async function main() {
  const c = new minio.Client({...})
  await c.initiateNewMultipartUpload('test', 'oo', {})
  const uploadID = await c.findUploadId("test", 'oo')
  console.log(uploadID)
}
main().catch(e => {
  throw e
})

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@prakashsvmx