[C++][Compute] Dispatch* should examine options as well as input types

Function::Dispatch* should have access to options as well as argument types.

This will allow kernel authors to write kernels which are specific to certain configurations of options. Otherwise we may be leaving performance on the table when for example a function's output could be contiguously preallocated, but only for the default FunctionOptions. Currently the author would have no choice but to choose the lowest-common-denominator flags for the kernel.

In another vein, "cast" is currently a MetaFunction instead of a ScalarFunction since it derives its output type from CastOptions. This requires a special case in Expressions since Expressions can only represent calls to scalar functions. Ideally a function which is semantically scalar like "cast" wouldn't need to resort to using a MetaFunction for dispatch

See also: https://github.com/apache/arrow/pull/10547#discussion_r654573800