mathlib3

5b90340b - feat(model_theory/terms_and_formulas): Notation for terms and formulas from Flypitch (#12630)

feat(model_theory/terms_and_formulas): Notation for terms and formulas from Flypitch (#12630) Introduces some notation, localized to `first_order`, to make typing explicit terms and formulas easier. Co-authored-by: Aaron Anderson <65780815+awainverse@users.noreply.github.com>