Added compare_scalar

[jorgecarleitao]

This PR adds a new function, arrow2::compute::comparison::compare_scalar with signature

compare_scalar(lhs: &dyn Array, rhs: &dyn Scalar, operator: Operator) -> Result<BooleanArray>

that compares a &dyn array with a &dyn scalar (error if not of the same datatype). This allows implementations to not have to select the right implementation based on the data_type.

All implementations of *_scalar were also stripped from the Result<>, since they were infallible (backward-incompatible).

Closes #316

[codecov]

Codecov Report

Merging #317 (beb56c6) into main (d278f08) will decrease coverage by 0.02%.
The diff coverage is 84.84%.

@@            Coverage Diff             @@
##             main     #317      +/-   ##
==========================================
- Coverage   80.55%   80.52%   -0.03%     
==========================================
  Files         324      324              
  Lines       21277    21369      +92     
==========================================
+ Hits        17140    17208      +68     
- Misses       4137     4161      +24     

Impacted Files	Coverage Δ
src/compute/comparison/utf8.rs	68.81% <60.00%> (-12.52%)	⬇️
src/compute/comparison/boolean.rs	63.75% <61.53%> (+0.59%)	⬆️
src/compute/comparison/primitive.rs	90.17% <84.61%> (-4.92%)	⬇️
src/compute/comparison/mod.rs	91.55% <89.10%> (-2.06%)	⬇️
src/scalar/primitive.rs	95.45% <0.00%> (+4.54%)	⬆️
src/scalar/mod.rs	66.66% <0.00%> (+21.21%)	⬆️

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