Improve error messages for Tensor and Text Document views

[grtlr]

What

Closes #8148.

This brings nicer error messages to mono component entities when multiple components were added.

@emilk This also improves the API of error_*, warning_label, and success_label in UiExt.

Checklist

• [x] I have read and agree to Contributor Guide and the Code of Conduct

• [x] I've included a screenshot or gif (if applicable)

• [x] I have tested the web demo (if applicable):

  • Using examples from latest main build: rerun.io/viewer
  • Using full set of examples from nightly build: rerun.io/viewer

• [x] The PR title and labels are set such as to maximize their usefulness for the next release's CHANGELOG

• [x] If applicable, add a new check to the release checklist!

• [x] If have noted any breaking changes to the log API in CHANGELOG.md and the migration guide

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[grtlr]

Done ✅