* add account to LeafsRequest

* add snapshot iterators

* step 1: read from the snapshot

* refactor: move FillAccounts to trie package

* add UT

* step 2: partial data from the snapshot

* tests: add snapshot cleanup

* bugfixes and nits

* pr comments: iterator key len and comments

* pr comments: test cleanup and renaming

* leafs_request: adding comments and reordering args

* leafs_request: fix grammar in comment

* refactor: move IncrOne to utils

* leafs_request: refactor and comment improvements

* add storage trie test

* test: move cleanup to test body

* add "done" check to prefixedIterator

* Readability improvements via builder struct

* iterator: add value

* bugfix (on ctx expiry)

* nits

* remove root check optimization

* add stat

* refactor: rb.readLeafsFromSnapshot

* Improve readability via a builder struct (#793)

* test: move cleanup to test body

* add "done" check to prefixedIterator

* Readability improvements via builder struct

* iterator: add value

* bugfix (on ctx expiry)

* nits

* remove root check optimization

* add stat

* refactor: rb.readLeafsFromSnapshot

* nits and more comments

* typo

* test: add assertRangeProofIsValid

* cleaner buffer allocation

* use sync pool for response allocations

* use snapshot.Tree to get iterators to the snapshot (#794)

* use snapshot.Tree to get iterators to the snapshot

* iterator wrappers to clean up code duplication

* minor simplification

* fix iterator Error call

* fix storage iterator creation to be thread safe

* use sync pool for snapKeys/snapVals

* handle late init. of sync'ed client snapshot

* pass proof around explicitly (#795)

* pass proof around explicitly

* close memdb on err paths

* bump min sync version (we changed LeafsRequest)

* Revert "use sync pool for snapKeys/snapVals"

This reverts commit f73138e0d36087962ae30a0b2c0b6a80f54e3a04.

* clear out slices before returning them to pool

* switch to using interface over passing Fn (#796)