[C++] Add "DispatchBest" APIs to compute::Function that selects a kernel that may require implicit casts to invoke

[asfimport]

Currently we have "DispatchExact" which requires an exact match of input types. "DispatchBest" would permit kernel selection with implicit casts required. Since multiple kernels may be valid when allowing implicit casts, we will need to break ties by estimating the "cost" of the implicit casts. For example, casting int8 to int32 is "less expensive" than implicitly casting to int64

Reporter: Wes McKinney / @wesm
Assignee: Ben Kietzman / @bkietz

Related issues:

• [C++] C++ array kernels framework and execution buildout (umbrella issue) (is a child of)
• [C++] Implement autocasting in arithmetic compute kernels (is duplicated by)
• [C++][Dataset] Improvements to implicit casting (is duplicated by)
• [C++] Reduce number of take kernels (relates to)
• [C++] Collapse Take APIs from 8 to 1 or 2 (relates to)

PRs and other links:

• GitHub Pull Request #9294

_{Note: This issue was originally created as ARROW-8919. Please see the migration documentation for further details.}

[asfimport]

Ben Kietzman / @bkietz:
Issue resolved by pull request 9294
#9294