[C++] Implement optimized "unsafe take" for use with selection vectors for kernel execution

[asfimport]

Selection vectors constructed from filters do not need to be subjected to boundschecking and other such safety checks as are present with a usual invocation of take. So based on the type width of a selection vector (uint16?) we should implement highly streamlined take implementations that additionally take into consideration that selection vectors are monotonic by construction

Reporter: Wes McKinney / @wesm
Assignee: Wes McKinney / @wesm

Related issues:

• [C++] C++ array kernels framework and execution buildout (umbrella issue) (is a child of)
• [C++] Improve and expand Take/Filter benchmarks (is related to)

_{Note: This issue was originally created as ARROW-8903. Please see the migration documentation for further details.}

[asfimport]

Wes McKinney / @wesm:
This was done in ARROW-5760 and there are benchmarks for monotonic takes