refactor logout in client so we don't need a fully loaded session

instead, we pass the session id in
this will make it easier to first dispose the client when leaving the
/session/<id> and just creating a client without fully loading it
to log out. This way sync is already not running anymore.

src/matrix/Client.js

@@ -386,10 +386,21 @@ export class Client {
         return !this._reconnector;
     }
 
-    logout() {
+    startLogout(sessionId) {
         return this._platform.logger.run("logout", async log => {
+            this._sessionId = sessionId;
+            log.set("id", this._sessionId);
+            const sessionInfo = await this._platform.sessionInfoStorage.get(this._sessionId);
+            if (!sessionInfo) {
+                throw new Error(`Could not find session for id ${this._sessionId}`);
+            }
             try {
-                await this._session?.logout(log);
+                const hsApi = new HomeServerApi({
+                    homeserver: sessionInfo.homeServer,
+                    accessToken: sessionInfo.accessToken,
+                    request: this._platform.request
+                });
+                await hsApi.logout({log}).response();
             } catch (err) {}
             await this.deleteSession(log);
         });

src/matrix/Session.js

@@ -109,11 +109,6 @@ export class Session {
         return this._sessionInfo.userId;
     }
 
-    /** @internal call Client.logout instead */
-    async logout(log = undefined) {
-        await this._hsApi.logout({log}).response();
-    }
-
     // called once this._e2eeAccount is assigned
     _setupEncryption() {
         // TODO: this should all go in a wrapper in e2ee/ that is bootstrapped by passing in the account