[C++] Reduce generated code in vector_hash.cc

[asfimport]

Since hashing doesn't need to know about logical types, we can do the following:

• Use same generated code for both BinaryType and StringType (and LargeBinary/LargeString)

• Use same generated code for primitive types having the same byte width

  These two changes should reduce binary size and improve compilation speed

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++] Reduce shared library / binary code size (umbrella issue) (is related to)

PRs and other links:

• GitHub Pull Request #7528

_{Note: This issue was originally created as ARROW-8933. Please see the migration documentation for further details.}

[asfimport]

Wes McKinney / @wesm:
Issue resolved by pull request 7528
#7528