Stop TextTruncator from briefly showing full text before shave.js truncates it

[jonboiser]

Summary

1. Adds an inline style to the top-level div of TextTruncator that limits the height and hides the overflow of the untruncated text prop before shave.js can work on it. These styles are removed after shave.js has completed its work.
2. Cancels the debounced updateTitle calls during the beforeDestroy hook so the code isn't executed later when the component is unmounted (creating a lot of logs in the console).

Screengrabs from TE - China

Before

After

There is a slight change after shave.js works, but much more subtle than before

References

Fixes #7982

Reviewer guidance

Find a channel where nodes have long descriptions like Touchable Earth or CK-12. You should be able to browse the Lesson Creation workflow without seeing the issues in #7982

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Testing checklist

• Contributor has fully tested the PR manually
• If there are any front-end changes, before/after screenshots are included
• Critical user journeys are covered by Gherkin stories
• Critical and brittle code paths are covered by unit tests

PR process

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• PR has 'needs review' or 'work-in-progress' label
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• If this is an important user-facing change, PR or related issue has a 'changelog' label
• If this includes an internal dependency change, a link to the diff is provided

Reviewer checklist

• Automated test coverage is satisfactory
• PR is fully functional
• PR has been tested for accessibility regressions
• External dependency files were updated if necessary (yarn and pip)
• Documentation is updated
• Contributor is in AUTHORS.md

[nucleogenesis]

LGTM!