feat: consolidate xml parse logic

[njbrake]

Description

Consolidates the XML parsing logic to reduce code duplication

PR Type

• 💅 Refactor

Relevant issues

Checklist

• I understand the code I am submitting.
• I have added unit tests that prove my fix/feature works
• I have run this code locally and verified it fixes the issue.
• New and existing tests pass locally
• Documentation was updated where necessary
• I have read and followed the contribution guidelines
• AI Usage:
  • No AI was used.
  • AI was used for drafting/refactoring.
  • This is fully AI-generated.

AI Usage Information

• AI Model used: Opus 4.5
• AI Developer Tool used: Claude Code + AoE
• Any other info you'd like to share: At first claude insisted on backwards compatibility (aka not removing any utils files but using those files to just re-export the now shared util. I told it to delete the files.

When answering questions by the reviewer, please respond yourself, do not copy/paste the reviewer comments into an AI system and paste back its answer. We want to discuss with you, not your AI :)

[codecov]

Codecov Report

❌ Patch coverage is 78.75000% with 17 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...rc/any_llm/providers/openai/xml_reasoning_utils.py	77.77%	1 Missing and 5 partials ⚠️
src/any_llm/providers/openai/xml_reasoning.py	85.71%	3 Missing and 1 partial ⚠️
src/any_llm/providers/minimax/minimax.py	66.66%	2 Missing ⚠️
src/any_llm/providers/portkey/portkey.py	66.66%	2 Missing ⚠️
src/any_llm/providers/sambanova/sambanova.py	66.66%	2 Missing ⚠️
src/any_llm/providers/llamafile/llamafile.py	50.00%	1 Missing ⚠️

Files with missing lines	Coverage Δ
src/any_llm/providers/huggingface/huggingface.py	77.86% <100.00%> (-7.41%)	⬇️
src/any_llm/providers/mistral/mistral.py	90.62% <100.00%> (-7.81%)	⬇️
src/any_llm/providers/llamafile/llamafile.py	87.17% <50.00%> (-2.57%)	⬇️
src/any_llm/providers/minimax/minimax.py	60.41% <66.66%> (-29.06%)	⬇️
src/any_llm/providers/portkey/portkey.py	66.66% <66.66%> (-20.84%)	⬇️
src/any_llm/providers/sambanova/sambanova.py	75.00% <66.66%> (-11.45%)	⬇️
src/any_llm/providers/openai/xml_reasoning.py	85.71% <85.71%> (ø)
...rc/any_llm/providers/openai/xml_reasoning_utils.py	77.77% <77.77%> (ø)

... and 37 files with indirect coverage changes

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[njbrake]

Mistral released an SDK update yestereday that broke out type here

[njbrake]

Integration tests: https://github.com/mozilla-ai/any-llm/actions/runs/21489970373