feat: lake: input dependencies

[tydeu]

This PR adds input_file and input_dir as new target types. It also adds the needs configuration option for Lean libraries and executables. This option generalizes extraDepTargets (which will be deprecated in the future), providing much richer support for declaring dependencies across package and target type boundaries.

Closes #2761.

[ghost]

Mathlib CI status (docs):

• ❗ Mathlib CI can not be attempted yet, as the nightly-testing-2025-03-27 tag does not exist there yet. We will retry when you push more commits. If you rebase your branch onto nightly-with-mathlib, Mathlib CI should run now. You can force Mathlib CI using the force-mathlib-ci label. (2025-03-28 05:19:05)