chore: enable no-non-null-assertion internally, excluding tests#8019

JoshuaKGoldberg merged 8 commits intotypescript-eslint:maintypescript-eslint/typescript-eslint:mainfrom

JoshuaKGoldberg:lint-enable-no-non-null-assertionJoshuaKGoldberg/typescript-eslint:lint-enable-no-non-null-assertionCopy head branch name to clipboard