This makes the default behavior consistent between SpriteBase3D,
BaseMaterial3D and imported glTF scene materials.
Alpha scissor threshold property hints now allows for more precise
adjustments as well.
Clean up and do fixes to hash functions and newly introduced murmur3 hashes in #61934
* Clean up usage of murmur3
* Fixed usages of binary murmur3 on floats (this is invalid)
* Changed DJB2 to use xor (which seems to be better)
* Map is unnecessary and inefficient in almost every case.
* Replaced by the new HashMap.
* Renamed Map to RBMap and Set to RBSet for cases that still make sense
(order matters) but use is discouraged.
There were very few cases where replacing by HashMap was undesired because
keeping the key order was intended.
I tried to keep those (as RBMap) as much as possible, but might have missed
some. Review appreciated!
Add "generate_mipmap" font import option.
Add some missing features to the Sprite3D.
Move BiDi override code from Control to TextServer.
Add functions to access TextServer font cache textures.
Add MSDF related flags and shader to the standard material.
Change standard material cache to use HashMap instead of Vector.
