FIX: Propagate record conversion errors as PyErr in DBNDecoder

[wtn]

DBNDecoder.decode() panicked on record conversion failure because the inner push_rec called .unwrap() on into_py_any(py).

This change extracts push_rec to module scope with return type PyResult<()> so errors propagate to the Python caller instead.

Motivation: The existing code was not breaking, but had a comment referencing a clippy bug. I found that the clippy behavior is OK, so I fixed up the code here.

Type of change

• Bug fix (non-breaking change which fixes an issue)

How has this change been tested?

I ran tests locally and with a regression test (not necessary to keep permanently).

Checklist

• My code builds locally with no new warnings (scripts/build.sh)
• My code follows the style guidelines (scripts/lint.sh and scripts/format.sh)
• New and existing unit tests pass locally with my changes (scripts/test.sh)
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works (not applicable)

Declaration

I confirm this contribution is made under an Apache 2.0 license and that I have the authority
necessary to make this contribution on behalf of its copyright owner.