feat(xml-builder): use DOMParser for browser XML parsing

[kuhe]

Issue

#3979

Description

Uses window.DOMParser in browsers instead of fast-xml-parser

Testing

new unit tests, also ran all of our existing S3 tests with the browser bundle, confirming that it is using the replacement.

Checklist

• If the PR is a feature, add integration tests (*.integ.spec.ts).
  • XML parsing is only used on the response, at which point unit tests do the same job
• [n/a] If you wrote E2E tests, are they resilient to concurrent I/O?
• [n/a] If adding new public functions, did you add the @public tag and enable doc generation on the package?

[kuhe]

• update root level aggregate unit and browser tests to exclude/include the xml-parser test file

[trivikr]

Protocol tests need to be updated to use DOMParser

• Codegen https://github.com/smithy-lang/smithy-typescript/blob/434dd9c93329166b6bacdc54adb20511f6460575/smithy-typescript-codegen/src/main/java/software/amazon/smithy/typescript/codegen/HttpProtocolTestGenerator.java#L606-L611
• Usage

  aws-sdk-js-v3/private/aws-protocoltests-restxml/package.json

  Line 65 in 2922063

  "fast-xml-parser": "5.2.5",

It can be done in alternative PR as a PoC, and merged, before taking up this change.