Consider warning/error if "Disabled" plugin combined with explicit installation
We received reports of users confused that the effect of (essentially):

```
new ApolloServer({
  plugins: [
    ApolloServerPluginUsageReporting({ some: 'custom configuration' }),
    ApolloServerPluginUsageReportingDisabled(),
  ],
})
```

is to leave usage reporting on despite the "disabled" plugin. We should consider just making this into an error (which would be sorta-backwards-incompatible but only sorta, this was not intended to have well-defined semantics, and AS4 is new anyway), or perhaps a warning although warnings easily just become spam.

(The "disabled" plugins actually mean "disable the automatic installation of the corresponding plugin with default configuration" but currently has no effect if you manually install the corresponding plugin.)