feat(field_theory/adjoin): Compact elements of `intermediate_field` (#15438)
feat(field_theory/adjoin): Compact elements of `intermediate_field` (#15438)

This PR proves some lemmas regarding compact elements of `intermediate_field`, essentially copying the analogous results for `submodule` from `linear_algebra/span.lean`. This PR combos with #15419.



Co-authored-by: tb65536 <25c750517795e47f172dc8c552ed72c7de260bd4@users.noreply.github.com>
Co-authored-by: Yury G. Kudryashov <2c59405d0ec2e119a1c3d2318bdb4a6ce50051ae@urkud.name>

leanprover-community/mathlib,leanprover-community/mathlib