Refactor logging system to use exchange for targeted client notifications

[tzolov]

Bug description
The current MCP logging implementation has several limitations:

• Logging notifications are broadcast to all connected clients regardless of their interest level
• There's a single global minimum logging level for the entire server
• Clients cannot individually configure which log levels they want to receive
• The current approach is inefficient as it sends unnecessary messages to clients

This design doesn't align with the per-session approach used for other MCP features like sampling and roots, where each client can have its own configuration.

Expected behavior

• Use the exchange mechanism to send logging notifications only to specific client sessions
• Track minimum logging level per client session rather than globally
• Filter logging notifications at the server side based on each client's configured level
• Change setLoggingLevel from a notification to a request/response pattern for proper acknowledgment
• Deprecate the old broadcasting behavior.

Acceptance Criteria

• Each client can set its own minimum logging level
• Logging notifications below a client's minimum level are filtered out
• Logging notifications at or above a client's minimum level are delivered
• Ddd integration tests

Environment
Affects all MCP versions including 0.9.0-SN

Related to #97

[damien-urruty-sonarsource]

Hello @tzolov,

I have a few questions/comments regarding this change. Our server does a bunch of things at startup and we would like to print some logs to the client.

1. How can we log something before any specific exchange was initiated? I think the only way to receive a McpSyncServerExchange instance is in a handler (e.g. tool or resource handler).
2. Why was the broadcasting behavior deprecated? I think both mechanisms are complementary, you could want some messages to target only a specific client, but some others to be broadcasted
3. Can I still log things after the exchange happened? E.g. by keeping this instance around. The problem is that I wouldn't know when the client is gone

Thanks