Make Transform::rotate_axis and Transform::rotate_local_axis use Dir3

[mweatherley]

Objective

Related to #12981

Presently, there is a footgun where we allow non-normalized vectors to be passed in the axis parameters of Transform::rotate_axis and Transform::rotate_local_axis. These methods invoke Quat::from_axis_angle which expects the vector to be normalized. This PR aims to address this.

Solution

Require Dir3-valued axis parameters for these functions so that the vector's normalization can be enforced at type-level.

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Migration Guide

All calls to Transform::rotate_axis and Transform::rotate_local_axis will need to be updated to use a Dir3 for the axis parameter rather than a Vec3. For a general input, this means calling Dir3::new and handling the Result, but if the previous vector is already known to be normalized, Dir3::new_unchecked can be called instead. Note that literals like Vec3::X also have corresponding Dir3 literals; e.g. Dir3::X, Dir3::NEG_Y and so on.

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Discussion

This axis input is unambigiously a direction instead of a vector, and that should probably be reflected and enforced by the function signature. In previous cases where we used, e.g., impl TryInto<Dir3>, the associated methods already implemented (and required!) additional fall-back logic, since the input is conceptually more complicated than merely specifying an axis. In this case, I think it's fairly cut-and-dry, and I'm pretty sure these methods just predate our direction types.

[alice-i-cecile]

Yep, this predates our Dir3 type :) I agree with using the strict Dir3 here: the normalization is required.