Fix leaf expression reconciliation (#22971)

## Which issue does this PR close?

- Closes #22955

## Rationale for this change

This fixes a bug with the extract leaf expressions

## What changes are included in this PR?

This is a one liner that sanity checks the schema is the same length
when we are doing expression pushdown

## Are these changes tested?

Yes, a couple of tests have been added.

## Are there any user-facing changes?

Nope!

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Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Co-authored-by: Adrian Garcia Badaracco <1755071+adriangb@users.noreply.github.com>

Author: 3 people