[Feature Request] Move the user-facing parts in temporalio.bridge.runtime to somewhere stable

[cretz]

Is your feature request related to a problem? Please describe.

Right now temporalio.bridge.runtime is used for telemetry and other things and we have intentionally left it in the unstable package

Describe the solution you'd like

Move it somewhere stable, probably either temporalio top level or temporalio.runtime or temporalio.common.