Towards completion of TexError tests

[zorkow]

Adds tests for errors in TeX packages in preparation of the l10n TexError rewrite. Note, that this is not fully complete coverage for all occurring TexErrors, but should be sufficient for the time being to actually work on the TexError refactoring.

In addition the PR adds:

• An Emacs .el script for ease of working with jest test output in Emacs. This is partially lifted from the old script in MathJax-Tests repository.
• Some tests to achieve complete coverage for packages: braket, unicode
• The old ConfigMacros tests.
• Updates tests that failed after merging PR #1106 .