workflows: add start tracing and match sampling

src/bitdrift_public/protobuf/matcher/v1/log_matcher.proto

@@ -55,11 +55,19 @@ message LogMatcher {
       state.v1.StateValueMatch state_value_match = 3 [(validate.rules).message.required = true];
     }
 
+    message SampledMatch {
+      // The % chance that a match will occur. This is the numerator of the percentage, with the
+      // denominator being 1,000,000. For example, if the value is 10,000, then 1% of matches will
+      // be sampled.
+      uint32 sample_rate = 1;
+    }
+
     oneof match_type {
       option (validate.required) = true;
       MessageMatch message_match = 1;
       TagMatch tag_match = 2;
       StateMatch state_match = 4;
+      SampledMatch sampled_match = 5;
     }
 
     reserved 3;

src/bitdrift_public/protobuf/workflow/v1/workflow.proto

@@ -190,8 +190,14 @@ message Workflow {
       ActionEmitSankeyDiagram action_emit_sankey_diagram = 3;
       ActionTakeScreenshot action_take_screenshot = 4;
       ActionGenerateLog action_generate_log = 5;
+      ActionStartTracing action_start_tracing = 6;
     }
 
+    // Specifies that the current session will start trace sampling. Tracing will stop when the
+    // workflow run ends. The exception to this is if the run results in a flush. If this happens,
+    // tracing will stay on until flush streaming completes.
+    message ActionStartTracing {}
+
     // Generates a new log message. This log will be injected into the workflow engine and processed
     // like any other log, either by this workflow or by another workflow.
     message ActionGenerateLog {