Add a new factory function : make_fixed_width_column()

[nvdbaranec]

Adds an overload to allocate_like() that takes raw inputs instead of deriving from an input column. The primary use case for this is callers of the form:

out column = caller(scalar, scalar, column);

where the type of the output column is derived from the scalar inputs, but the size comes from the column input. Concrete example:

copy_if_else(scalar lhs, scalar rhs, column boolean_mask)
{
   out = allocate_like(lhs.type(), mask.size());
}

[jrhemstad]

Instead of an allocate_like, this really should be a new factory:

unique_ptr<column> make_fixed_width_column(data_type type, size_type size, mask_state state, ...);

I originally split make_numeric_column and make_timestamp_column because I wasn't sure if the timestamp column would require additional arguments. But now that I've had some time to think about it, I'm pretty sure any additional arguments would be encapsulated into the data_type argument.

As such, I'd just make this code into the new factory.

[codecov]

Codecov Report

Merging #3461 into branch-0.12 will not change coverage.
The diff coverage is n/a.

@@             Coverage Diff              @@
##           branch-0.12    #3461   +/-   ##
============================================
  Coverage        87.35%   87.35%           
============================================
  Files               49       49           
  Lines             9329     9329           
============================================
  Hits              8149     8149           
  Misses            1180     1180

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[harrism]

Just realized this is in branch-0.12. Is it needed in branch-0.11?