ARROW-11503: [Rust][DataFusion] implement string splitting

[jwdeitch]

No description provided.

[github-actions]

https://issues.apache.org/jira/browse/ARROW-11503

[codecov-io]

Codecov Report

Merging #9437 (927e2c4) into master (a321cde) will decrease coverage by 0.00%.
The diff coverage is 72.09%.

@@ Coverage Diff @@## master #9437 +/- ##
==========================================
- Coverage 82.14% 82.14% -0.01% 
==========================================
Files 232 232 Lines 54150 54193 +43 ==========================================
+ Hits 44484 44516 +32 - Misses 9666 9677 +11 

Impacted Files	Coverage Δ
rust/datafusion/src/logical_plan/expr.rs	80.04% <0.00%> (-0.19%)	⬇️
...datafusion/src/physical_plan/string_expressions.rs	70.21% <54.16%> (-16.75%)	⬇️
rust/datafusion/src/physical_plan/functions.rs	72.75% <100.00%> (+0.46%)	⬆️
rust/datafusion/tests/sql.rs	99.85% <100.00%> (+<0.01%)	⬆️
rust/parquet/src/encodings/encoding.rs	95.05% <0.00%> (+0.19%)	⬆️

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[seddonm1]

Hi @jwdeitch

This overlaps with #9243 so maybe we can integrate the tests into a single PR?

[jwdeitch]

@seddonm1 ah good call, will do!