Problem:
We need to establish a pattern for `enable()`.
Solution:
- First `enable()` parameter is always `enable:boolean`.
- Update `vim.diagnostic.enable()`
- Update `vim.lsp.inlay_hint.enable()`.
- It was not released yet, so no deprecation is needed. But to help
HEAD users, it will show an informative error.
- vim.deprecate():
- Improve message when the "removal version" is a *current or older* version.
f1dfe32bf5
