Add log attribute limit configuration (#2861)

Fixes open-telemetry#2860

Adds log attribute limit configuration.

These new environment variables bring more consistency between spans and logs.

Author: alanwest

specification/common/README.md

@@ -91,11 +91,11 @@ limits programmatically. Names of the configuration options SHOULD be the same a
 in the list below.
 
 An SDK MAY implement model-specific limits, for example
-`SpanAttributeCountLimit`. If both a general and a model-specific limit are
-implemented, then the SDK MUST first attempt to use the model-specific limit, if
-it isn't set, then the SDK MUST attempt to use the general limit. If neither are
-defined, then the SDK MUST try to use the model-specific limit default value,
-followed by the global limit default value.
+`SpanAttributeCountLimit` or `LogRecordAttributeCountLimit`. If both a general
+and a model-specific limit are implemented, then the SDK MUST first attempt to
+use the model-specific limit, if it isn't set, then the SDK MUST attempt to use
+the general limit. If neither are defined, then the SDK MUST try to use the
+model-specific limit default value, followed by the global limit default value.
 
 #### Configurable Parameters