This commit also adds means to manually disable warnings
in `code` tags where it's a false positive with the new
`skip-lint` attribute.
Warnings are now enabled on CI to prevent future errors.
We don't use that info for anything, and it generates unnecessary diffs
every time we bump the minor version (and CI failures if we forget to
sync some files from opt-in modules (mono, text_server_fb).
* Typo fixes.
* Navigation agent's `velocity_computed` signal is not emitted by
`set_velocity`, but at the end of that frame if `set_velocity` is
called.
* Simplify link in navigation agent's `avoidance_enabled` description.
* Unify `navigation_layers` description across `NavigationAgent{2,3}D`.
* Unify `is_normalized()` description across `Vector2`, `Vector3`, and
`Vector4`
The main change is to caculate tangent directly from bezier curve, without going
through discretized polyline, avoiding pitfalls of discretization. A similar refacor
had been applied to Curve3D.
The test cases for Curve2D is updated, comparing floating point with is_equal_approxmiate()
instead of `==`, in order to avoid float precision problem.