Refactor embedding input/output getter/setter (#39339)
* simplify common get/set
* remove some noise
* change some 5 years old modeling utils
* update examples
* fix copies
* revert some changes
* fixes, gah
* format
* move to Mixin
* remove smolvlm specific require grad
* skip
* force defaults
* remodularise some stuff
* remodularise more stuff
* add safety for audio models
* style
* have a correct fallback, you daft donkey
* remove this argh
* change heuristic for audio models
* fixup
* revert
* this works
* revert again
* ðŸ§
* aaah ESM has two modelings aaah
* add informative but short comment
* add `input_embed_layer` mixin attribute
* style
* walrus has low precedence
* modular fix
* this was breaking parser
