Make "-B all" apply to plugin streams as well.

testing/btest/plugins/debug-streams-all.js

@@ -0,0 +1,12 @@
+/*
+ * Verify that `-B all` leads to plugin debug stream content in debug.log.
+ * This requires JavaScript and a debug build.
+ * @TEST-REQUIRES: test "$($BUILD/zeek-config --build_type)" = "debug"
+ * @TEST-REQUIRES: $SCRIPTS/have-javascript
+ * @TEST-EXEC: zeek -b -B all %INPUT
+ * @TEST-EXEC: grep -q '[plugin Zeek::JavaScript]' debug.log
+ */
+
+zeek.on('zeek_init', () => {
+  console.log('Hello Zeek!');
+});