[C++] Remove ambiguous constructor for VectorKernel

[asfimport]

The VectorKernel class currently has two constructors for kernels that only a KernelSignature and an ArrayKernelExec - one with just the two arugments, and one with default argument values. 

Trying to use them results in an ambiguous call error like this:

/home/zagto/Code/arrow/cpp/src/arrow/compute/kernels/vector_run_length_encode.cc: In function 'void arrow::compute::internal::Register
VectorRunLengthEncode(arrow::compute::FunctionRegistry*)':
/home/zagto/Code/arrow/cpp/src/arrow/compute/kernels/vector_run_length_encode.cc:137:34: error: call of overloaded 'VectorKernel(std::
shared_ptr<arrow::compute::KernelSignature>&, std::function<arrow::Status(arrow::compute::KernelContext*, const arrow::compute::ExecBa
tch&, arrow::Datum*)>&)' is ambiguous
 137 |     VectorKernel kernel(sig, exec);
     |                                  ^
In file included from /home/zagto/Code/arrow/cpp/src/arrow/compute/function.h:27,
                from /home/zagto/Code/arrow/cpp/src/arrow/compute/api_vector.h:23,
                from /home/zagto/Code/arrow/cpp/src/arrow/compute/kernels/vector_run_length_encode.cc:1:
/home/zagto/Code/arrow/cpp/src/arrow/compute/kernel.h:616:3: note: candidate: 'arrow::compute::VectorKernel::VectorKernel(std::shared_
ptr<arrow::compute::KernelSignature>, arrow::compute::ArrayKernelExec, arrow::compute::KernelInit, arrow::compute::VectorFinalize)'
 616 |   VectorKernel(std::shared_ptr<KernelSignature> sig, ArrayKernelExec exec,
     |   ^~~~~~~~~~~~
/home/zagto/Code/arrow/cpp/src/arrow/compute/kernel.h:607:3: note: candidate: 'arrow::compute::VectorKernel::VectorKernel(std::shared_
ptr<arrow::compute::KernelSignature>, arrow::compute::ArrayKernelExec)'
 607 |   VectorKernel(std::shared_ptr<KernelSignature> sig, ArrayKernelExec exec)
     |   ^~~~~~~~~~~~

Reporter: Tobias Zagorni / @zagto
Assignee: Tobias Zagorni / @zagto

PRs and other links:

• GitHub Pull Request #13235

_{Note: This issue was originally created as ARROW-16659. Please see the migration documentation for further details.}

[asfimport]

Weston Pace / @westonpace:
Issue resolved by pull request 13235
#13235