feat: flag on TermInfo to force rendering of term in hover

[mhuisi]

This PR adds a field isDisplayableTerm to TermInfo and all utility functions which create TermInfo that can be set to force the language server to render the term in hover popups.

[leanprover-community-bot]

Mathlib CI status (docs):

• ❗ Batteries CI can not be attempted yet, as the nightly-testing-2025-10-16 tag does not exist there yet. We will retry when you push more commits. If you rebase your branch onto nightly-with-mathlib, Batteries CI should run now. You can force Mathlib CI using the force-mathlib-ci label. (2025-10-16 15:00:36)

[leanprover-bot]

Reference manual CI status:

• ❗ Reference manual CI can not be attempted yet, as the nightly-testing-2025-10-16 tag does not exist there yet. We will retry when you push more commits. If you rebase your branch onto nightly-with-manual, reference manual CI should run now. You can force reference manual CI using the force-manual-ci label. (2025-10-16 15:00:38)