[C++] Implement autocasting in arithmetic compute kernels

[asfimport]

Arithmetic compute kernels should autocast arguments when possible similar to how dataset expressions autocast arguments (e.g. arrow::compute::Add(float_array, int_array)) should cast the integer array to a float before adding if possible)

Reporter: Jonathan Keane / @jonkeane
Assignee: Ben Kietzman / @bkietz

Related issues:

• [C++] Arithmetic kernels for numeric arrays (is a child of)
• [C++] Add "DispatchBest" APIs to compute::Function that selects a kernel that may require implicit casts to invoke (duplicates)

_{Note: This issue was originally created as ARROW-11078. Please see the migration documentation for further details.}