fix: allow error deserializers to populate error response body

[kuhe]

Currently, deserializer collectors read response body streams prior to attempting to deserialize them.

If there is a parsing error, such as when a JSON service front end layer (load balancer, CDN, etc) has an error and returns non-JSON, the raw text of this error is lost since the stream collector has read the stream.

For this PR, addressing such cases, if the error contains a field called $responseBodyText, it will be written over the response body's (consumed and therefore empty) stream, so the user can read the body text instead of only having an empty stream.

It is up to the deserializer implementation to write the body text to this field.

Example:

export const parseJsonBody = (streamBody: any, context: SerdeContext): any =>
  collectBodyString(streamBody, context).then((encoded) => {
    if (encoded.length) {
      try {
        return JSON.parse(encoded);
      } catch (e: any) {
        if (e?.name === "SyntaxError") {
          Object.defineProperty(e, "$responseBodyText", {
            value: encoded,
          });
        }
        throw e;
      }
    }
    return {};
  });

export const parseXmlBody = (streamBody: any, context: SerdeContext): any =>
  collectBodyString(streamBody, context).then((encoded) => {
    if (encoded.length) {
      const parser = new XMLParser({
        attributeNamePrefix: "",
        htmlEntities: true,
        ignoreAttributes: false,
        ignoreDeclaration: true,
        parseTagValue: false,
        trimValues: false,
        tagValueProcessor: (_: any, val: any) => (val.trim() === "" && val.includes("\n") ? "" : undefined),
      });
      parser.addEntity("#xD", "\r");
      parser.addEntity("#10", "\n");

      let parsedObj;
      try {
        parsedObj = parser.parse(encoded);
      } catch (e: any) {
        if (e && typeof e === "object") {
          Object.defineProperty(e, "$responseBodyText", {
            value: encoded,
          });
        }
        throw e;
      }

      const textNodeName = "#text";
      const key = Object.keys(parsedObj)[0];
      const parsedObjToReturn = parsedObj[key];
      if (parsedObjToReturn[textNodeName]) {
        parsedObjToReturn[key] = parsedObjToReturn[textNodeName];
        delete parsedObjToReturn[textNodeName];
      }
      return getValueFromTextNode(parsedObjToReturn);
    }
    return {};
  });

[kuhe]

related to aws/aws-sdk-js-v3#5851