Trie simplification. (#2815)

* switch to simple codec, trie broken for now

* Actualy use trie_root_noext

* align some hash, failing test on EMCH comment

* Fix trie code over layout instead of hash, revert legacy code for legacy
mainnet ??

* stub behind LayOut

* fix no_std

* temp solution for legacy trie behind feature legacy-key in various crate

* use remote project

* rc client db need prefix

* update trie deps

* bum spec runtime version

* Removing legacy as default.

* Switch mode to non legacy.

* bump runtime version

* Remove legacy trie compatibility features.

* fix warning

* bump version

* change hash on new test.

* Move dependency (#11 trie PR) patched to a parity repo.
Bench reverted to correct hasher.
Some renaming and doc improvments.

* ChildBitmap renaming to BitMap.

* Renaming of LayOut to Layout.

* formatting.

* Removing abreviation such as _ix nb_ or bm.

* Update deps and apply renaming 'Buff' -> 'Buffer'.

* Align to latest trie crates naming changes.

* Update trie dependency.

* Update trie dependency.

* change block_import test hash

* update trie deps (trie use new scale codec but it does not seems to be
an issue).

* update to use latest trie version (no mgmt of multiple radix).

* tabify

* Restoring test to 10 000.

* Use published crate, trie bench is currently down until publishing
(require another pr to update version).

* Update trie-bench.