Fix stopped monitoring threads

[sergiyvamz]

Summary

Fix stopped monitoring threads

Description

• Improve exception logging in monitoring thread
• Increase monitoring thread idle time to 10min
• Make sure getting an existing monitor, creating a new monitor, and destroying a monitor are well-synchronized.
• Avoid caching a reference to monitor object since it may be destroyed; use weak pointer instead.
• Avoid storing and then reusing of idle/stopped monitors

Additional Reviewers

@karenc-bq
@aaron-congo
@crystall-bitquill
@aaronchung-bitquill

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.