fix: avoid memory leak when redeploying pgjdbc

FAST_NUMBER_FAILED is used as a control-flow-exception pattern, thus it does not require a stacktrace.
It turns out Throwable might store strong reference to a class, thus it might result in OutOfMemory

closes #394

org/postgresql/jdbc2/AbstractJdbc2ResultSet.java

@@ -2217,7 +2217,18 @@ public long getLong(int columnIndex) throws SQLException
     * the exception is always caught and is not visible to users.
     */
    private static final NumberFormatException FAST_NUMBER_FAILED = 
        new NumberFormatException();
        new NumberFormatException() {

            // Override fillInStackTrace to prevent memory leak via Throwable.backtrace hidden field
            // The field is not observable via reflection, however when throwable contains stacktrace, it does
            // hold strong references to user objects (e.g. classes -> classloaders), thus it might lead to
            // OutOfMemory conditions.
            @Override
            public synchronized Throwable fillInStackTrace()
            {
                return this;
            }
        };

    /**
     * Optimised byte[] to number parser.  This code does not