feat：support trim clause

[idersec]

• Do only one thing
• Non breaking API changes
• Tested

What did this pull request do?

You can use trim clause to remove the keywords at the beginning or end of a SQL segment, including and,or,xor,,

User Case Description

type TrimTest interface {
// TestTrim
//
// select * from @@table where
//    {{trim}}
//        {{for _, name :=range list}}
//            name = @name or
//        {{end}}
//    {{end}}
TestTrim(list []string)[]gen.T
}

[jinzhu]

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[jinzhu]

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