Use new taxon metrics in API

[mdoering]

For releases and imported external datasets the backend now has [taxon metrics](Use new taxon metrics).
The tree API has slightly changed and the countBy rank parameter is removed. Species counts will now always be present in the existing count property. The existing TreeNode datasetSectors map property is replaced by an int array of source dataset keys in sourceDatasetKeys.

• adapt assembly tree and portal tree component:
  • to show the species counts
  • use TreeNode.sourceDatasetKeys instead of datasetSectors map

[mdoering]

see CatalogueOfLife/portal#23

[mdoering]

metrics is on dev now, but only exist for the datasets imported since that deployment, e.g. donalds:
https://www.dev.checklistbank.org/dataset/2207/classification?taxonKey=2

[mdoering]

When browsing the tree there are 2 calls being done when opening a node. One for the children and one does an automplete search - I assume to populate the search box above. Can that be populated by the tree directly somehow?