[Backport 2.x] Add TIMEDIFF and DATEDIFF functions. (#131)

[opensearch-trigger-bot]

Backport 438c44d from #1195

[codecov-commenter]

Codecov Report

Merging #1234 (438c44d) into 2.x (de79815) will increase coverage by 0.00%.
The diff coverage is 100.00%.

❗ Current head 438c44d differs from pull request most recent head f0ae82c. Consider uploading reports for the commit f0ae82c to get more accurate results

@@            Coverage Diff            @@
##                2.x    #1234   +/-   ##
=========================================
  Coverage     98.32%   98.33%           
- Complexity     3555     3575   +20     
=========================================
  Files           346      344    -2     
  Lines          8768     8819   +51     
  Branches        554      559    +5     
=========================================
+ Hits           8621     8672   +51     
  Misses          142      142           
  Partials          5        5           

Flag	Coverage Δ
sql-engine	98.33% <100.00%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...expression/function/RelevanceFunctionResolver.java	100.00% <ø> (ø)
...ch/sql/planner/optimizer/LogicalPlanOptimizer.java	100.00% <ø> (ø)
...rg/opensearch/sql/analysis/ExpressionAnalyzer.java	100.00% <100.00%> (ø)
...a/org/opensearch/sql/data/model/ExprDateValue.java	100.00% <100.00%> (ø)
...g/opensearch/sql/data/model/ExprDatetimeValue.java	100.00% <100.00%> (ø)
...a/org/opensearch/sql/data/model/ExprTimeValue.java	100.00% <100.00%> (ø)
.../opensearch/sql/data/model/ExprTimestampValue.java	100.00% <100.00%> (ø)
.../org/opensearch/sql/data/model/ExprValueUtils.java	100.00% <100.00%> (ø)
...c/main/java/org/opensearch/sql/expression/DSL.java	100.00% <100.00%> (ø)
...arch/sql/expression/datetime/DateTimeFunction.java	100.00% <100.00%> (ø)
... and 36 more

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.