Inversify is a required dependency for non-webview extension code

[tortmayr]

Due to the utility inversify functions provided with @eclipse-glsp/protocol we have introduced a direct dependency to
inversify/reflect-metadata in the non-webview part of a GLSP vscode integration.

We don't use inversify in the extension code but still need the dependencies and the reflect-metadata imports due to the transitive
dependency of @eclipse-glsp/protocol.
Maybe we should consider to extract the inversify utilities into a separate package (e.g. @eclipse-glsp/di or @eclipse-glsp/inversify).
We could then reexport the symbols provided by this package in @eclipse-glsp/sprotty same as we do for @eclipse-glsp/protocol.
This would remove the dependency requirement in vscode (host) extensions and in addition, it would be possible to use those utilities in other projects without consuming the rest of @eclipse-glsp/protocol.