fix(config): list on/off in getBool's expected-values error message

ConfigView.getBool accepts true/false and on/off, but its invalid-value
error read "(expected true, false)", under-reporting the accepted forms
(e.g. lazy_connect=on is valid yet the message implies otherwise). List
all four, matching getBoolOnOff's convention of naming exactly what it
accepts.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: bluestreak01

core/src/main/java/io/questdb/client/impl/ConfigView.java

@@ -111,7 +111,7 @@ public boolean getBool(String key, boolean dflt) {
         if ("false".equals(v) || "off".equals(v)) {
             return false;
         }
-        throw new IllegalArgumentException("invalid " + key + ": " + v + " (expected true, false)");
+        throw new IllegalArgumentException("invalid " + key + ": " + v + " (expected true, false, on, off)");
     }
 
     public boolean getBoolOnOff(String key, boolean dflt) {