[java-spanner] custom WatchdogProvider executor service

Hi.
It was found that we have one "Cloud-Spanner-WatchdogProvider-0" thread per Spanner service
For example we have around 180 clients = 180 instance of spanner and such threads. 1 thread approximately takes 1 mb off-heap memory so, these threads consume resources.
Previously we have similar problem with Cloud-Spanner-TransportChannel, but there is a possibility to set a custom executor while creating spanner service.
Is there possibility to provide custom executor for watchdog provider? Currently I don't see such possibility.

Environment details
Java version: 8
Spanner Java Library Version: 6.38.2