Miscellaneous QoL repo updates

[sdadn]

Summary

This PR makes the following updates to the repo:

• Cleans up .gitignore by reducing the list to relevant entries. It also adds. *.tgz so that test packages from npm pack won't get committed.
• Breaks out the eslint and stylelint config into their separate files to reduce bloat in package.json.
• Removes babel plugins as they are already installed through the babel presets.
• Updates root devDependency version format for better clarity.

Testing

This change was tested using:

• WDIO
• Jest
• Visual testing (please attach a screenshot or recording)
• Other (please describe below)
• No tests are needed

This was tested by running the linter commands and ensuring that no additional files are staged for commit after the .gitignore updates.

Reviews

In addition to engineering reviews, this PR needs:

• UX review
• Accessibility review
• Functional review

Additional Details

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Thank you for contributing to Terra.
@cerner/terra