Give linalg elementwise functions a proper definition and signature

[Balint-R]

Right now, our code is structured like this:

def _gen_elementwise_unary_macro(op: DefinedOpCallable) -> CallMacro:
    @CallMacro.generate()
    def op_macro(visitor: ToMLIRBase, x: Compiled) -> Tensor | MemRef:
        ...
    
    return op_macro

exp = _gen_elementwise_unary_macro(mlir_linalg.exp)
log = _gen_elementwise_unary_macro(mlir_linalg.log)
abs = _gen_elementwise_unary_macro(mlir_linalg.abs)
...

However, we could instead restructure it like this:

def _elementwise_unary(op: DefinedOpCallable, visitor: ToMLIRBase, x: Tensor | MemRef) -> Tensor | MemRef:
    ...

@CallMacro.generate()
def exp(visitor: ToMLIRBase, x: Compiled) -> Tensor | MemRef:
    """
    exp documentation
    """
    return _elementwise_unary(mlir_linalg.exp, visitor, x)


@CallMacro.generate()
def log(visitor: ToMLIRBase, x: Compiled) -> Tensor | MemRef:
    """
    log documentation
    """
    return _elementwise_unary(mlir_linalg.log, visitor, x)

where we no longer have a function that returns a CallMacro, but just call the inner function directly (_elementwise_unary should have the same behaviour as op_macro).

This results in a bit more code, but in the long term, it might be better, because we can nicely add a different docstring to each function and it's also easier to see their signature.