collect threads count in opentelemetry-instrumentation-system-metrics (open-telemetry#1339)

* collect threads count in opentelemetry-instrumentation-system-metrics

* update

* avoid devidedByZero exception when sawp memory is 0

* add ut

* change log

* lint

* lint

Co-authored-by: Srikanth Chekuri <[email protected]>

Author: 2 people

CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased](https://github.com/open-telemetry/opentelemetry-python/compare/v1.13.0-0.34b0...HEAD)
 
+### Added
+
+- `opentelemetry-instrumentation-system-metrics` add supports to collect system thread count. ([#1339](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/1339))
+
 ## [1.13.0-0.34b0](https://github.com/open-telemetry/opentelemetry-python/releases/tag/v1.13.0-0.34b0) - 2022-09-26
 
 
@@ -102,7 +106,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   ([#1253](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/1253))
 - Add metric instrumentation in starlette
   ([#1327](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/1327))
-  
+
 
 ### Fixed