Update Magnum and m.css to latest

Motivation and Context

Note: Requires https://github.com/facebookresearch/habitat-lab/pull/1776 in order to pass the CI. The lab PR can be merged independently, as the syntax should work even with the original code.

Another ~2 months worth of Magnum features, fixes and improvements. What's new since #2278:

Fixed compatibility with Emscripten 3.1.49+
Fixed Matrix::isOrthogonal() to catch negative dot product values. Note that this effectively tightens up certain assertions and could cause previously-incorrect but seemingly working code to assert (or raise an exception in Python). Thanks to @jturner65 for the discovery.
New Math::join() overload that joins a range and a point, in addition to joining two ranges. Requested by @jturner65.
Low-level refactoring in the Math library, resulting in better runtime perf in debug builds and most Vector operators being now constexpr
New Quaternion::rotation() overload for creating a rotation from one vector to another. Matches Eigen's Quaternion::setFromTwoVectors() and similar APIs in other quaternion libraries. Related to #2301, it felt better to just put this in Magnum instead of having to maintain a utility function in Habitat.
Made the GlslangShaderConverter plugin work with glslang 14.0. Not directly used in Habitat, but affects various packages where it is enabled by default, such as Homebrew, where a build failure was hit by @eundersander.
New MAGNUM_BUILD_PYTHON_BINDINGS_RTLD_GLOBAL CMake option for Python bindings. Enabled by default for static builds, performs sys.setdlopenflags(sys.getdlopenflags()|ctypes.RTLD_GLOBAL) before loading native modules in an attempt to resolve cursed issues with deduplicating globals across shared modules that was made impossible by Python implicitly isolating each loaded module into its namespace, which was repeatedly hit by @eundersander, @0mdc and others. I'm writing very long sentences today, yes, sorry.
Exposed trade.MeshAttributeData and trade.SceneFieldData classes to Python, which together with meshtools.interleave() and scenetools.combine_fields() finally allows trade.MeshData and trade.SceneData to be created from scratch in pure Python. Which in turn opens possibilities for adding new attributes to existing meshes, such as annotating skinned meshes with bone influences. Or for building whole scene hierarchies from loose meshes, materials and such, and exporting those to glTF. This was also the last main blocker that prevented writing the batch renderer composite file generation pipeline (#1969) in pure Python.

Also updated the m.css submodule, because apparently it was untouched since December 2022(!):

Fixed compatibility with newer docutils
Fixed compatibility with dvisvgm < 3.0 and Ghostscript 10
Improved highlighting of ANSI-colored terminal output
Ability to style <video> tags the same as images
Detecting new builtins in Python 3.11 and omitting them from output if they're not overriden and documented by the user
No longer using deprecated distutils, thus fixing compatibility with Python 3.12
Recognizing / and * in pybind11 signatures (which is used heavily by new Magnum bindings, such as SceneFieldData constructors)

How Has This Been Tested

:green_circle:

facebookresearch / habitat-sim

Update Magnum and m.css to latest #2309

Motivation and Context

How Has This Been Tested