improve documentation truncation behavior

[kuhe]

You can see that some shapes get quite long, CLI example: https://docs.aws.amazon.com/cli/latest/reference/quicksight/update-template.html

JSv3 API example: https://docs.aws.amazon.com/AWSJavaScriptSDK/v3/latest/clients/client-quicksight/classes/updatetemplatecommand.html

---

This PR aims to improve the recently implemented structural hint doc generation.

• more aggressive truncation for repeated shapes

• truncated item shows the target shape name instead of its entire structure

  • the name appears earlier in the shape hint

example, original shape appearance with name tag and then subsequent repeated shape truncation

{
  myShape: { // MyShape
    field1: "STRING_VALUE",
    field2: "STRING_VALUE"
  },
  myShape2: "<MyShape>"
}

JSv3 diff in https://github.com/aws/aws-sdk-js-v3/pull/4585/files

[syall]

Could test cases be added for truncating on both occurrences and depth?