keep attrs in idata/datatree conversions

[OriolAbril]

Description

closes #2474

Checklist

• Does the PR follow official PR format?
• Does the PR include new or updated tests to prevent issue recurrence (using pytest fixture pattern)?
• Is the code style correct (follows pylint and black guidelines)?
• Is the fix listed in the Maintenance and fixes
  section of the changelog?

---

📚 Documentation preview 📚: https://arviz--2476.org.readthedocs.build/en/2476/

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.83%. Comparing base (01c8b94) to head (0a0adb7).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2476   +/-   ##
=======================================
  Coverage   86.82%   86.83%           
=======================================
  Files         124      124           
  Lines       13014    13016    +2     
=======================================
+ Hits        11300    11303    +3     
+ Misses       1714     1713    -1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

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

[OriolAbril]

should be ready to merge and I think we can make a release next week to include this and the caching fix when reading files