[C++] Implement string space trimming kernels: trim, ltrim, and rtrim

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Reporter: Wes McKinney / @wesm
Assignee: Maarten Breddels / @maartenbreddels

Related issues:

• [C++] String algorithm library for StringArray/BinaryArray (is a child of)
• [C++] Caching pre computed data based on FunctionOptions in the kernel state (relates to)
• [C++] Add scalar string slicing/substring extract kernel (is required by)

PRs and other links:

• GitHub Pull Request #8621

_{Note: This issue was originally created as ARROW-9128. Please see the migration documentation for further details.}

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Wes McKinney / @wesm:
I'm gonna tackle this tomorrow (Wednesday) probably

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Uwe Korn / @xhochy:
In Python these routines are called `strip, any reasons for going for trim` here?

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Antoine Pitrou / @pitrou:
SQL and Postgres have trim /  ltrim / rtrim it seems, I suppose that explains the names proposed here.

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Maarten Breddels / @maartenbreddels:
Shall I implement this?

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Antoine Pitrou / @pitrou:
This is unassigned, so you can definitely take it up.

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Antoine Pitrou / @pitrou:
Issue resolved by pull request 8621
#8621