Tune Text.trim, fix for Text.split

[jdunkerley]

Pull Request Description

• Rename Location.Start to Location.Left.
• Rename Location.End to Location.Right.
• Use auto-scoping for Location.
• Tune widgets for Text.trim.
• Correct signature of Text.split.
• Adjist generateLocallyUniqueIdent to not fail on bad signature.

Checklist

Please ensure that the following checklist has been satisfied before submitting the PR:

• The documentation has been updated, if necessary.
• Screenshots/screencasts have been attached, if there are any visual changes. For interactive or animated visual changes, a screencast is preferred.
• All code follows the
  Scala,
  Java,
  TypeScript,
  and
  Rust
  style guides. In case you are using a language not listed above, follow the Rust style guide.
• Unit tests have been written where possible.

[jdunkerley]

Closes #10446.