Fixes #6938: Integrated terminal non-falsey shell exit codes should be reported to the UI, not just the console

[chrmarti]

Replacing console.error with the regular error message.

[mention-bot]

@chrmarti, thanks for your PR! By analyzing the annotation information on this pull request, we identified @Tyriar and @kisstkondoros to be potential reviewers

[msftclas]

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[Tyriar]

I don't think Terminal: is necessary here, doesn't seem to be used elsewhere (from a cursory search of Severity.Error).

[Tyriar]

Generally good practice to keep first line of git commit messages under 50 characters, more detail underneath (for future ref 😃).