5) rust: use borrow in compute interface

[crop2000]

the current compute function signature looks like this:

	pub fn compute(&mut self, count: usize, inputs: &[&[FaustFloat]], outputs: &mut [&mut [FaustFloat]]){

this prevents us from passing a mutable reference as input buffer slice.
in the case one wants to chain dsps where the outputs of one dsp are used as the input of another it would be good if one can pass pass same slice that is used as the output of one dsp as input of another. but in that case one would pass a mutable reference. which is not possible with the current function signature.
this pr changes the functions to be more general. so that one can pass a mutable reference to the the input.
The new now looks like this:

	pub fn compute<InType, OutType>(
		&mut self,
		count: usize,
		inputs: impl borrow::Borrow<[InType]>,
		mut outputs: impl borrow::BorrowMut<[OutType]>,
	) where
		InType: borrow::Borrow<[FaustFloat]>,
		OutType: borrow::BorrowMut<[FaustFloat]>,
	{

this change is fully backwards compatible.

Because I found out that my earlier introduced compute_array interface is not contributing to the performance i removed it here again because it would make this change more complicated.