Refactory of Fork-Tree data structure (#11228)

* Iterative version of some fork-tree methods

* Prune doesn't require its generic args to be 'clone'

* Fork-tree import and drain-filter iterative implementations

* Fork-tree map iterative implementation

* Optimization of some operations, e.g. rebalance only when required

* Destructuring assignments not supported yet by stable rustc 1.57

* Safe implementation of 'map' and 'drain_filter' methods

* Remove dummy comment

* Trigger CI pipeline

* Test map for multi-root fork-tree and refactory of `find_node_index_where`

* Fix find node index with predicate

* Nits

* Tree traversal algorithm is not specified

* Move unspecified tree traversal warning to 'map'

* Immutable 'drain_filter' predicate

* Apply suggestions from code review

* Remove double mapping

Co-authored-by: André Silva <[email protected]>