Avoids NoClassDefFoundError: Could not initialize class DDSpanLink$EncoderHolder in Graal native-image (#8036)

Both fromJson and toJson methods need to be registered, do the same for other JSON entries to be consistent.

Also declare some JsonRule types need reflective access for a related issue using DD_TRACE_SAMPLING_RULES

Author: mcculls

dd-java-agent/agent-bootstrap/src/main/resources/META-INF/native-image/com.datadoghq/dd-java-agent/reflect-config.json

@@ -38,24 +38,42 @@
   {
     "name" : "datadog.trace.agent.common.sampling.SpanSamplingRules$RuleAdapter",
     "methods": [
-      {"name": "fromJson"}
+      {"name": "fromJson"},
+      {"name": "toJson"}
     ]
   },
+  {
+    "name" : "datadog.trace.agent.common.sampling.SpanSamplingRules$JsonRule",
+    "allDeclaredConstructors" : true,
+    "allPublicConstructors" : true,
+    "allDeclaredFields" : true,
+    "allPublicFields" : true
+  },
   {
     "name" : "datadog.trace.agent.common.sampling.TraceSamplingRules$RuleAdapter",
     "methods": [
-      {"name": "fromJson"}
+      {"name": "fromJson"},
+      {"name": "toJson"}
     ]
   },
+  {
+    "name" : "datadog.trace.agent.common.sampling.TraceSamplingRules$JsonRule",
+    "allDeclaredConstructors" : true,
+    "allPublicConstructors" : true,
+    "allDeclaredFields" : true,
+    "allPublicFields" : true
+  },
   {
     "name" : "datadog.trace.agent.core.TracingConfigPoller$TracingSamplingRulesAdapter",
     "methods": [
-      {"name": "fromJson"}
+      {"name": "fromJson"},
+      {"name": "toJson"}
     ]
   },
   {
     "name" : "datadog.trace.agent.core.DDSpanLink$SpanLinkAdapter",
     "methods": [
+      {"name": "fromSpanLinkJson"},
       {"name": "toSpanLinkJson"}
     ]
   },