[BUG] Some text functions are not work as expected

[LantaoJin]

Is your feature request related to a problem?
NonFallbackCalciteTextFunctionIT. testAscii
NonFallbackCalciteTextFunctionIT. testLeft
NonFallbackCalciteTextFunctionIT. testLocate
NonFallbackCalciteTextFunctionIT. testReplace
NonFallbackCalciteTextFunctionIT. testStrcmp
NonFallbackCalciteTextFunctionIT. testSubstr

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[LantaoJin]

cc @xinyual

[xinyual]

For these questions, we miss them since they are not on the doc https://github.com/opensearch-project/sql/blob/2.x/docs/user/ppl/functions/string.rst. Can you please give a full list of string functions so I can check whether I miss more?