`@metamask/eslint-config` has been updated to v4.1.0. This update
requires that we update `eslint` to v7 as well, which in turn requires
updating most `eslint`-related packages.
Most notably, `babel-eslint` was replaced with `@babel/eslint-parser`,
and `babel-eslint-plugin` was replaced by `@babel/eslint-plugin`. This
required renaming all the `babel/*` rules to `@babel/*`.
Most new or updated rules that resulted in lint errors have been
temporarily disabled. They will be fixed and re-enabled in subsequent
PRs.