static convertToConfigObject(fieldName, value) {
    const configObject = {};
    let last = configObject;
    let searchIndex = 0;
    let nameStart = 0;
    while (true) {
      const idx = fieldName.indexOf('.', searchIndex);
      if (idx < 0) {
        break;
      }
      if (idx == 0 || fieldName[idx - 1] != '\\') {
        const part = fieldName.substring(nameStart, idx).replace(/\\\./g, '.');
        last[part] = {};
        last = last[part];
        nameStart = idx + 1;
      }
      searchIndex = idx + 1;
    }

    last[fieldName.substring(nameStart).replace(/\\\./g, '.')] = value;
    return configObject;
  }
Convert config from ('fieldName', value) format to a partial config object.

E. g. from ('manifest.retryParameters.maxAttempts', 1) to
{ manifest: { retryParameters: { maxAttempts: 1 }}}.

@param {string} fieldName
@param {*} value
@return {!Object}
@export