Optimize Restconf-Netconf operations for List and Leaf-List items

When new list elements are inserted via Restconf/Netconf (topology connected device) each list element is processed in a separate edit-config request causing significant performance impact.

For example if there is PUT of a new element with insert=first into a list of 10 items, then there will be 1 (`replace` for new item) + 10 * 2 (`remove` + `replace` for each earlier item) = 21 netconf requests as a part of single restconf transaction.

See NetconfRestconfTransaction.java -> createImpl() and replaceImpl() methods, 
removeImpl() and deleteImpl() expected to be updated via NETCONF-1177

It seems reasonable to move list recognition (and conversion into multiple elements within same request) to NetconfDataTreeService implementation (netconf-client-mdsal) -> see AbstractNetconfDataTreeService

Alternatively or in addition the NetconfDataTreeService API can be extended to accept multiple data nodes, not single node per request.

The NetconfRestconfTransaction to be adjusted accordingly