Fix partial-no-import message to include more accurate rule name (#…

…1019)

By this change, the rule message will be properly associated with the rule name. See the examples below:

Before:

```sh-session
$ echo '@import "file.scss"' | npx stylelint

<input css ZECpLj>
       ✖  The 'partial-no-import' rule won't work if linting in a code string without an actual file

✖ 1 problem (1 error, 0 warnings)
```

After:

```sh-session
$ echo '@import "file.scss"' | npx stylelint

<input css PE6AAM>
  1:2  ✖  This rule won't work if linting in a code string without an actual file  scss/partial-no-import

✖ 1 problem (1 error, 0 warnings)
```

In addition, this change updates `jest-preset-stylelint` to use `testRule()` instead of `postcss`.
Because `testRule()` is closer to the actual use of `stylelint` and easier to avoid any potential troubles.
See https://github.com/stylelint/jest-preset-stylelint/releases/tag/7.1.0

package.json

@@ -25,7 +25,7 @@
     "github-contributors-list": "^1.2.5",
     "husky": "^9.0.11",
     "jest": "^29.7.0",
-    "jest-preset-stylelint": "^7.0.1",
+    "jest-preset-stylelint": "^7.1.0",
     "lint-staged": "^14.0.1",
     "np": "^10.0.6",
     "postcss": "^8.4.39",