Decouple vuex-toolkit from sagas and extend Store in a backward-compatible way

[banderror]

Decouple vuex-toolkit from sagas. Implement vuex saga plugin as a vuex-toolkit-saga "extension" - a separate package.

Create an extended Store interface. Something like

interface VuexToolkitStore<S> extends Store<S> {
  run: RunSaga;
  send: SendMessage;
}

Create 2 versions of the send() method (maybe send and put, or send and resolve - naming to be decided). One should be synchronous and return void, the other one should be async and return a Promise. Both should work with all kinds of messages that vuex-toolkit supports.