Replace own xml parser with sphinx-test-reports

[MaximilianSoerenPollak]

What

Replacing our own XML parser with sphinx-test-reports xml parser to simplify the code we own and make maintenance easier.

Acceptance Criteria (DoD)

• Have no functional difference.
• Delete/reduce all xml parsing & other code relevant to it in our own source code
• Be able to have only partial tests passed (so we can have only the tests relevant to the bundle be parssed).
  => This might be an incremental step and come in as a 2nd part of a PR or so.

How

No response