Implement 'process.runtime.*' attributes for resources

Implement support for the the 'process.runtime.name',
'process.runtime.version' and 'process.runtime.description'
as specified in the resource semantic convensions for
processes.

Closes #2659

Author: Michele Mancioppi

opentelemetry-sdk/src/opentelemetry/sdk/resources/__init__.py

@@ -43,7 +43,10 @@
     )
     print(trace.get_tracer_provider().resource.attributes)
 
-    {'telemetry.sdk.language': 'python',
+    {'process.runtime.name': 'cpython',
+    'process.runtime.version': '3.8.6',
+    'process.runtime.description': '3.8.6 (default, Sep 30 2020, 04:00:38) [GCC 10.2.0]'
+    'telemetry.sdk.language': 'python',
     'telemetry.sdk.name': 'opentelemetry',
     'telemetry.sdk.version': '0.13.dev0',
     'service.name': 'shoppingcart',
@@ -243,8 +246,17 @@ def __hash__(self):
 
 
 _EMPTY_RESOURCE = Resource({})
+_runtime_version = ".".join(map(
+    str,
+    implementation.version[:3]
+    if implementation.version.releaselevel == "final" and not implementation.version.serial
+    else implementation.version
+))
 _DEFAULT_RESOURCE = Resource(
     {
+        PROCESS_RUNTIME_NAME: implementation.name,
+        PROCESS_RUNTIME_VERSION: _runtime_version,
+        PROCESS_RUNTIME_DESCRIPTION: sys.version,
         TELEMETRY_SDK_LANGUAGE: "python",
         TELEMETRY_SDK_NAME: "opentelemetry",
         TELEMETRY_SDK_VERSION: _OPENTELEMETRY_SDK_VERSION,