SessionQuotaManagingDataStore should not bind session when removing pages

[theigl]

SessionQuotaManagingDataStore currently binds the session as a side-effect when removeAllPages or removePage is called.

Both methods call IPageContext.getSessionData(key, supplier) which in the case of DefaultPageContext, binds the session:

https://github.com/apache/wicket/blob/a20a38c0068b4f926386bfb2c9dd46a470ff4baa/wicket-core/src/main/java/org/apache/wicket/pageStore/DefaultPageContext.java#L77-L89

The removePage and removeAllPages methods should probably do nothing if the session has not been bound yet.