chore: Move cast to spark-expr crate

[andygrove]

Which issue does this PR close?

Part of #630

Rationale for this change

Move another expr to the new spark-expr crate.

What changes are included in this PR?

Just moving code around. No functional changes.

Specific changes

• Move spark_cast function from utils.rs to cast.rs to keep all cast code together
• Move some utility functions from core crate into datafusion_comet_utils
• Move cast.rs into datafusion_comet_spark_expr

How are these changes tested?

Existing tests

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 53.82%. Comparing base (8274a61) to head (6d1e697).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##               main     #654   +/-   ##
=========================================
  Coverage     53.82%   53.82%           
  Complexity      811      811           
=========================================
  Files           106      106           
  Lines         10242    10242           
  Branches       1917     1917           
=========================================
  Hits           5513     5513           
  Misses         3752     3752           
  Partials        977      977           

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[viirya]

I think these functions are specified to Spark cast. Maybe they should be with cast expression in spark-expr crate?

[andygrove]

array_with_timezone is also called from some other expressions in temporal.rs. Once all the expressions are moved to the new crate then maybe we can move some of these utility functions there as well.

[andygrove]

I suppose some of these functions could just live in the spark-expr crate. I will look at that as a follow on issue.