Part of #18610.
Our intent is to move `definePlugin`, `defineRule`, and `eslintCompatPlugin` to a separate package `@oxlint/plugins` (plural to avoid confusion with naming convention for plugins `oxlint-plugin-xxx`).
So rename the current entry point which exports these functions from `oxlint/plugin` to `oxlint/plugins` (plural).
As we prepare for alpha release of JS plugins, it feels like we can remove the warning logged to stderr.
```
WARNING: JS plugins are experimental and not subject to semver.
Breaking changes are possible while JS plugins support is under development.
```
They do still remain experimental, but I don't think we need to shout that quite as loudly now.
This is technically breaking (only for types), but custom plugins are experimental.
The ruletester/defineRule/definePlugin are re-exported but with a `@deprecated` tag which I think is a good enough trade off
I want to avoid users bringing in a ton of custom plugin code when doing `import { defineConfig } from 'oxlint'`
It'd be better if the path of the specific invalid config were printed when this happened, in case I'm using nested configs, but for now this improves things a bit, at least.
A couple of changes to how plugin names are dealt with:
### Package names
Don't use package name if the specifier used to load the plugin is a relative path.
If your project is called `super-server`, and you load a plugin from `../plugins/no-foo.js`, that plugin shouldn't be called `super-server` - that's the name of the project, not the plugin.
Now it throws an error, telling you to give the plugin a name.
### Ensure `context.id` matches the plugin name
Previously `context.id` might not match the actual plugin name (it could include e.g. `eslint-plugin-` prefix, for example). Now it always matches.
This required re-implementing `normalize_plugin_name` on JS side too.
### Tests
Add a bunch of tests for every combination I could imagine of `plugin.meta.name`, package name, and alias. Those tests make sure `context.id` is same as the plugin name on Rust side.
### Incomplete
There's 2 things remaining to get naming completely correct:
1. Support plugin names with slashes in them e.g. `@scope/eslint-plugin-name` (#14557).
2. It's possible for the same plugin to have different names in different places, because you can alias the same plugin twice with different names in a config, and an override. Plugin names (in `context.id`, and in `// oxlint-disable` comments) should reflect the plugin name *as it is in the config which enabled that rule*.
I'm leaving those 2 for now.
overlookmotel