make helper error types generics (#7878)

* make helper error types generics

* avoid From<io::Error> dep in runner helper logic

* slip of the pen, bump futures to 0.3.9

* more generics

* generic var spaces

Co-authored-by: Andronik Ordian <write@reusable.software>

* network-gossip: add metric for number of local messages (#7871)

* network-gossip: add metric for number of local messages

* grandpa: fix GossipEngine missing metrics registry parameter

* network-gossip: increase known messages cache size

* network-gossip: fix tests

* grandpa: remove unnecessary clone

Co-authored-by: Max Inden <mail@max-inden.de>

* network-gossip: count registered and expired messages separately

* network-gossip: add comment on known messages cache size

* network-gossip: extend comment with cache size in memory

Co-authored-by: Max Inden <mail@max-inden.de>

* Clean-up pass in network/src/protocol.rs (#7889)

* Remove statistics system

* Remove ContextData struct

* Remove next_request_id

* Some TryFrom nit-picking

* Use constants for peer sets

* contracts: Don't read the previous value when overwriting a storage item (#7879)

* Add `len` function that can return the length of a storage item efficiently

* Make use of the new len function in contracts

* Fix benchmarks

* cargo run --release --features=runtime-benchmarks --manifest-path=bin/node/cli/Cargo.toml -- benchmark --chain=dev --steps=50 --repeat=20 --pallet=pallet_contracts --extrinsic=* --execution=wasm --wasm-execution=compiled --heap-pages=4096 --output=./frame/contracts/src/weights.rs --template=./.maintain/frame-weight-template.hbs

* Remove unused imports

Co-authored-by: Parity Benchmarking Bot <admin@parity.io>

* Fix clear prefix check to avoid erasing child trie roots. (#7848)

* Fix clear prefix check to avoid erasing child trie roots.

* Renaming and extend existing test with check.

* last nitpicks.

* use follow paths to std standarad components

* line width

Co-authored-by: Bernhard Schuster <bernhard@parity.io>
Co-authored-by: Andronik Ordian <write@reusable.software>
Co-authored-by: André Silva <123550+andresilva@users.noreply.github.com>
Co-authored-by: Max Inden <mail@max-inden.de>
Co-authored-by: Pierre Krieger <pierre.krieger1708@gmail.com>
Co-authored-by: Alexander Theißen <alex.theissen@me.com>
Co-authored-by: Parity Benchmarking Bot <admin@parity.io>
Co-authored-by: cheme <emericchevalier.pro@gmail.com>