feat: add Session api for stateful connection and set role support

[shivanshuraj1333]

fixes: #1443

please check the end to end implementation with this toy program https://github.com/shivanshuraj1333/clickhuose-test

make sure to update the go.mod to point to the changes present in this PR

Summary:

• Problem: ClickHouse Go driver lacks support for SET ROLE functionality due to connection pooling, which doesn't maintain connection state across multiple statements.

• Solution: Added session management API that provides stateful connections while maintaining backward compatibility.

Key Changes

• New Session Interface: Added Session interface with SetRole(), UnsetRole(), and Close() methods
• Connection Enhancement: Added AcquireSession() method to main connection interface

Implementation:

• session struct for native driver
• stdSession struct for standard SQL driver
• Proper resource management and error handling

example usage:

// Acquire a stateful session
session, err := conn.AcquireSession()
if err != nil {
    return err
}
defer session.Close()

// Set role for this session
if err := session.SetRole("admin"); err != nil {
    return err
}

// Execute queries - role persists across operations
rows, err := session.Query("SELECT currentUser()")
// ... more operations

// Unset role when done
session.UnsetRole()