What is actually required in `plugin.xml`?

[Documentation of `plugin.xml`](https://cordova.apache.org/docs/en/9.x/plugin_ref/spec.html) unfortunately doesn't define which of the tags are really required, only what attributes of a tag are.

But a good part of the non-function information (name, description, version, license, keywords, repo, issue) is duplicated in `package.json`.

Can we maybe get rid of some of these in the core plugins for simplified plugin maintenance?

(Breaking compatibility with older Cordova CLI / tooling / platform versions would be fine, we can set that via `engines.cordovaDependencies` in `package.json` if needed - but probably not anyway.)