Refactor(plugins): Improve thread safety for avdschema

[ClausHolbechArista]

Change Summary

Improve thread safety for avdschema

Related Issue(s)

When running schema validation in multiple threads at the same time (only seen with pyavd), the schema tooling fails with errors like:

...
  File "/home/holbech/.local/lib/python3.10/site-packages/pyavd/validate_inputs.py", line 44, in validate_inputs
    return eos_designs_schema_tools.validate_data(inputs)
  File "/home/holbech/.local/lib/python3.10/site-packages/pyavd/avd_schema_tools.py", line 78, in validate_data
    raise exception
pyavd.vendor.errors.errors.AvdSchemaError: dictionary changed size during iteration

This happens because the original schema object was updated with resolved dynamic keys as well as schema references during the validation.

Proposed changes

By preserving the original schema and instead work on local copies the validation becomes more thread safe (more issues may exist).

How to test

Tested with nornir and running validation for all devices across multiple threads at the same time.

Checklist

User Checklist

• N/A

Repository Checklist

• My code has been rebased from devel before I start
• I have read the CONTRIBUTING document.
• My change requires a change to the documentation and documentation have been updated accordingly.
• I have updated molecule CI testing accordingly. (check the box if not applicable)

[Shivani-chourasiya]

LGTM!