[Backport 2.x] Fix truncate() function

[opensearch-trigger-bot]

Backport 7714819 from #1197

[codecov-commenter]

Codecov Report

Merging #1213 (e14cca1) into 2.x (13474e3) will decrease coverage by 35.55%.
The diff coverage is n/a.

@@              Coverage Diff              @@
##                2.x    #1213       +/-   ##
=============================================
- Coverage     98.32%   62.76%   -35.56%     
=============================================
  Files           346       10      -336     
  Lines          8760      658     -8102     
  Branches        555      119      -436     
=============================================
- Hits           8613      413     -8200     
- Misses          142      192       +50     
- Partials          5       53       +48     

Flag	Coverage Δ
query-workbench	62.76% <ø> (?)
sql-engine	?

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

Impacted Files	Coverage Δ
...h/sql/expression/function/OpenSearchFunctions.java
...expression/function/RelevanceFunctionResolver.java
...ssion/operator/arthmetic/MathematicalFunction.java
...ript/filter/lucene/relevance/SingleFieldQuery.java
...pensearch/sql/ppl/parser/AstExpressionBuilder.java
...java/org/opensearch/sql/sql/parser/AstBuilder.java
...pensearch/sql/sql/parser/AstExpressionBuilder.java
...ensearch/sql/expression/function/FunctionName.java
...org/opensearch/sql/data/type/WideningTypeRule.java
...nsearch/storage/script/ExpressionScriptEngine.java
... and 346 more

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