Added system.stack_trace table for server thread introspection

Why it matters

This feature allows developers and DBAs to introspect the current state of the ClickHouse server by examining stack traces of all active threads. It helps in debugging, performance analysis, and diagnosing issues by providing insight into thread execution at any given moment.

How to use it

Query the system.stack_trace table using a standard SELECT statement to retrieve stack trace information of all server threads. For example:

SELECT * FROM system.stack_trace;