Runtime: Pass instanceID to drivers.Open for use in telemetry

[begelundmuller]

Refactors the drivers.Open function signature:

// New
Open(instanceID string, config map[string]any, client *activity.Client, logger *zap.Logger) (Handle, error)

// Previous
Open(config map[string]any, shared bool, client *activity.Client, logger *zap.Logger) (Handle, error)

The shared bool args is replaced by a convention that a connection is considered shared if instanceID == "" (this is clarified in docstrings throughout the PR).

This change enables capturing the instanceID when a connection is opened (e.g. for use in telemetry). Previously, it had to be captured in the connection's As... functions (as added in this PR), which is prone to race conditions, which are currently causing race tests to fail on main (example).