NRD rules and "recent" kernel pos index (#3302)

* variants for output_pos linked list entries (head/tail/middle/unique)
next and prev and Vec<u8> lmdb keys

* get_pos on enum

* break list and list entries out into separate enums

* track output features in the new output_pos index, so we can determine coinbase maturity

* push entry impl for none and unique

* some test coverage for output_pos_list

* commit

* wip - FooListEntry

* use instance of the index

* linked list of output_pos and commit_pos both now supported

* linked_list

* cleanup and rename

* rename

* peek_pos

* push some, peek some, pop some

* cleanup

* commit pos
cleanup

* split list and entry out into separate db prefixes

* cleanup and add placeholder for pop_back

* pop_pos_back (for popping off the back of the linked list)
test coverage for pop_pos_back

* wip

* placeholder for prune via a trait
pos must always increase in the index

* rewind kernel_pos_idx when calling rewind_single_block

* RewindableListIndex with rewind support.

* test coverage for rewindable list index

* test coverage for rewind back to 0

* rewind past end of list

* add tests for kernel_pos_idx with multiple commits

* commit

* cleanup

* hook NRD relative lock height validation into block processing and tx validation

* cleanup

* set local chain type for kernel_idx tests

* add test coverage for NRD rules in block processing

* NRD test coverage and cleanup

* NRD relative height 1 test

* test coverage for NRD kernels in block processing

* cleanup

* start of test coverage for txpool NRD kernel rules

* wip

* rework pool tests to use real chain (was mock chain) to better reflect reality (tx/block validation rules etc.)

* cleanup

* cleanup pruneable trait for kernel pos index

* add clear() to kernel_pos idx and test coverage

* hook kernel_pos rebuild into node startup, compaction and fast sync

* verify full NRD history on fast sync

* return early if nrd disabled

* fix header sync issue

api/src/handlers/utils.rs

@@ -26,7 +26,7 @@ use std::sync::{Arc, Weak};
 // boilerplate of dealing with `Weak`.
 pub fn w<T>(weak: &Weak<T>) -> Result<Arc<T>, Error> {
 	weak.upgrade()
-		.ok_or_else(|| ErrorKind::Internal("failed to upgrade weak refernce".to_owned()).into())
+		.ok_or_else(|| ErrorKind::Internal("failed to upgrade weak reference".to_owned()).into())
 }
 
 /// Internal function to retrieves an output by a given commitment