fix: make plugin-kit types usable in CommonJS

[fasttime]

Prerequisites checklist

• I have read the contributing guidelines.

What is the purpose of this pull request?

This PR ensures that the plugin-kit types can be imported from a CommonJS module when moduleResolution is one of 'node16' or 'nodenext'. This is currently not possible because of the way TypeScript handles imports of ESM modules in CommonJS.

Repro

What changes did you make? (Give an overview)

Made sure that packages/plugin/dist/cjs/index.d.cts uses the "resolution-mode": "import" import attribute to import ./types.ts.

- export type StringConfig = import("./types.ts").StringConfig;
- export type BooleanConfig = import("./types.ts").BooleanConfig;
+ export type StringConfig = import("./types.ts", { with: { "resolution-mode": "import" } }).StringConfig;
+ export type BooleanConfig = import("./types.ts", { with: { "resolution-mode": "import" } }).BooleanConfig;

It's not possible to add the import attribute directly to the source code in packages/plugin-kit/src/config-comment-parser.js because then the same import attribute would appear also in the generated ESM types, and jsr does not like that (maybe because import attributes are not supported in TypeScript < 5.0).

Downloading JSR release binary...
[00:15] [#################################################>] 40.8 MiB/40.9 MiB
Checking for slow types in the public API...
error: Failed preparing '@eslint/plugin-kit'.

Caused by:
    0: Failed to create a tarball
    1: Expected '{', got 'StringConfig' at file:///.../rewrite/packages/plugin-kit/dist/esm/index.d.ts:12:13
       
         export type StringConfig = import("./types.ts", { with: { "resolution-mode": "im...
                     ~~~~~~~~~~~~
Child process exited with: 1
npm error Lifecycle script `test:jsr` failed with error:
npm error code 1
npm error path .../eslint/rewrite/packages/plugin-kit
npm error workspace @eslint/[email protected]
npm error location .../eslint/rewrite/packages/plugin-kit
npm error command failed
npm error command sh -c jsr publish --dry-run

This is not the only possible fix, see also: eslint/json#66 (comment).

Other changes included in this PR:

• Made @eslint/core a runtime dependency of @eslint/plugin-kit.
• Added tests to ensure that @eslint/core and @eslint/plugin-kit can be imported from a .cts file.
• Added type tests to @eslint/plugin-kit.

Related Issues

Is there anything you'd like reviewers to focus on?