feat: add hint to deprecated linter

[wkrozowski]

This PR adds a clickable hint (and thus also a code action) to deprecated linter.

Awaiting nightly-with-mathlib that includes #14600.

[mathlib-lean-pr-testing]

Mathlib CI status (docs):

• ❗ Batteries/Mathlib CI will not be attempted unless your PR branches off the nightly-with-mathlib branch. Try git rebase c7eb8b5ec89d301726dffb7ee5be8bda9e57c3d5 --onto 3fc29d37a70f8fd904ebab848557c12383543008. You can force Mathlib CI using the force-mathlib-ci label. (2026-08-10 14:02:29)

[leanprover-bot]

Reference manual CI status:

• ❗ Reference manual CI will not be attempted unless your PR branches off the nightly-with-manual branch. Try git rebase c7eb8b5ec89d301726dffb7ee5be8bda9e57c3d5 --onto b1cd183c9978c3bedddc33baf7c9599baaeca046. You can force reference manual CI using the force-manual-ci label. (2026-08-10 14:02:32)