chore: missing `[coe]` attributes, review comments, fix tests

test: `norm_cast` and `push_cast`

chore: fix tests

Update src/Init/Data/Cast.lean

Co-authored-by: David Thrane Christiansen <david@davidchristiansen.dk>

Apply suggestions from code review

Co-authored-by: David Thrane Christiansen <david@davidchristiansen.dk>

use arxiv URL

move arxiv links out of doc-strings, into module-doc

remove inherit_doc; builtin_tactic already does this