Adding simulated logging and refactoring subscriptions to not need to track transports
* Updated architecture.md
* In server/index.ts
- remove import of Transport
- import beginSimulatedLogging and stopSimulatedLogging
- in clientConnected()
- change argument to sessionId? instead of transport
- add call to beginSimulatedLogging
- send server and sessionId to beginSimulatedResourceUpdates and beginSimulatedLogging
- in cleanup()
- add call to stopSimulatedLogging passing sessionId
* Added server/logging.ts
- Initialize logsUpdateIntervals to Map session ID to the interval for sending logging messages to the client
- in beginSimulatedLogging()
- create an array of logging meesages, customized with the sessionId if present
- if the interval for the sessionId hasn't been set, create one, calling server.sendLoggingMessage with a random message to the client each time the interval elapses
- in stopSimulatedLogging()
- if a logging interval exists for the sessionId, clear it and remove it
* In subscriptions.ts
- remove import of Transport
- remove transports map
- in beginSimulatedResourceUpdates()
- change arguments to server and sessionId
- check for the subsUpdateInterval for the session
- remove all transport storage and interaction
- instead use the server to send the notification
- in stopSimulatedResourceUpdates()
- remove management of transports map
* In sse.ts and streamableHttp.ts
- when calling clientConnected, pass sessionId instead of transport
* In stdio.ts,
- when calling clientConnected, pass nothing instead of transport
* In subscriptions.ts
- updated inline doc
