Implement new `apify-client-js` methods in Crawlee storages

[barjin]

Since in SDK we want to switch from custom implementation of getPublicUrl to calling the client implementations of those methods (see https://github.com/apify/apify-sdk-js/issues/433), we should add those methods to the local storage implementations in Crawlee as well.

The following methods are missing from the memory-storage in Crawlee (and are supported in apify-client-js):

For KVS:

+ createKeysPublicUrl
+ getRecordPublicUrl

For Dataset:

+ createItemsPublicUrl
+ getStatistics