Updating Text.repeat and adding Text.*

[jdunkerley]

Pull Request Description

Updating the Text.repeat function:

• fix issue with negative count
• add * operator

Add tests of the function.

Checklist

Please include the following checklist in your PR:

• The documentation has been updated if necessary.
• All code conforms to the Scala, Java, and Rust style guides.
• All code has been tested:
  • Unit tests have been written where possible.
  • If GUI codebase was changed: Enso GUI was tested when built using BOTH ./run dist and ./run watch.

[radeusgd]

Looks good, but IMO the negative values fix uncovers a deeper issue and we need to address it (in this PR or in a separate one).