Added Span limits support to the tracing SDK

- Added SpanLimits class
- TracerProvider now optionally accepts an instance of SpanLimits which
is passed all the way down to Spans.
- Spans use the limits to created bounded lists or dicts for different
fields.

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

@@ -919,11 +919,13 @@ def __init__(
         ],
         id_generator: IdGenerator,
         instrumentation_info: InstrumentationInfo,
+        span_limits: SpanLimits,
     ) -> None:
         self.sampler = sampler
         self.resource = resource
         self.span_processor = span_processor
         self.id_generator = id_generator
+        self._span_limits = span_limits
         self.instrumentation_info = instrumentation_info
         self._limits = None
 
@@ -1051,6 +1053,7 @@ def __init__(
             SynchronousMultiSpanProcessor, ConcurrentMultiSpanProcessor
         ] = None,
         id_generator: IdGenerator = None,
+        span_limits=None,
     ):
         self._active_span_processor = (
             active_span_processor or SynchronousMultiSpanProcessor()

opentelemetry-sdk/tests/trace/test_trace.py

@@ -42,8 +42,8 @@
 from opentelemetry.util._time import _time_ns
 
 
-def new_tracer() -> trace_api.Tracer:
-    return trace.TracerProvider().get_tracer(__name__)
+def new_tracer(span_limits=None) -> trace_api.Tracer:
+    return trace.TracerProvider(span_limits=span_limits).get_tracer(__name__)
 
 
 class TestTracer(unittest.TestCase):
@@ -1318,7 +1318,6 @@ def test_span_limits_env(self):
     def test_span_no_limits_env(self):
         # pylint: disable=protected-access
         num_links = int(trace._DEFAULT_SPAN_LINKS_LIMIT) + randint(1, 100)
-
         tracer = new_tracer()
         id_generator = RandomIdGenerator()
         some_links = [