Don't do plugin interface checks during code analysis

The plugin objects are MarshalByRefObject stubs, which means they
don't actually implement the interfaces we're checking for.  There's
some additional overhead to do the interface check.  We can avoid
it by doing the interface queries during initialization, and just
checking some bit flags later on.

Also, in the extension script info window, show a list of
implemented interfaces.

SourceGen/Sandbox/ScriptManager.cs

@@ -220,6 +220,20 @@ namespace SourceGen.Sandbox {
         }
         private void DebugGetScriptInfo(IPlugin plugin, StringBuilder sb) {
             sb.Append(plugin.Identifier);
+            sb.Append(":");
+
+            // The plugin is actually a MarshalByRefObject, so we can't use reflection
+            // to gather the list of interfaces.
+            // TODO(maybe): add a call that does the query on the remote site
+            if (plugin is PluginCommon.IPlugin_InlineJsr) {
+                sb.Append(" InlineJsr");
+            }
+            if (plugin is PluginCommon.IPlugin_InlineJsl) {
+                sb.Append(" InlineJsl");
+            }
+            if (plugin is PluginCommon.IPlugin_InlineBrk) {
+                sb.Append(" InlineBrk");
+            }
             sb.Append("\r\n");
         }
     }