state_machine no_std witness externalities (#6934)

* checkpoint before removing CT from change trie

* before trie backend without tx

* undo

* Started no transaction, but would need using a different root
calculation method, out of the scope of this pr, will roll back.

* Remove NoTransaction.

* partially address review.
dummy stats implementation for no_std.

* Remove ChangeTrieOverlay.

* modified function

* Remove witness_ext

* need noops changes root

* update from cumulus branch

* line break

* remove warning

* line break

* From review: renamings and stats active in no std (except time).

* include cache, exclude change trie cache with individual temporary bad looking
no_std check

* little test

* fuse imports and filter_map prepare_extrinsics_input_inner fold.

* put back ExtInner into Ext, awkward double proto for new function.

* Apply suggestions from code review

* Update primitives/state-machine/Cargo.toml

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

substrate/primitives/state-machine/src/stats.rs

@@ -17,8 +17,9 @@
 
 //! Usage statistics for state db
 
+#[cfg(feature = "std")]
 use std::time::{Instant, Duration};
-use std::cell::RefCell;
+use sp_std::cell::RefCell;
 
 /// Measured count of operations and total bytes.
 #[derive(Clone, Debug, Default)]
@@ -50,8 +51,10 @@ pub struct UsageInfo {
 	/// Memory used.
 	pub memory: usize,
 
+	#[cfg(feature = "std")]
 	/// Moment at which current statistics has been started being collected.
 	pub started: Instant,
+	#[cfg(feature = "std")]
 	/// Timespan of the statistics.
 	pub span: Duration,
 }
@@ -99,7 +102,9 @@ impl UsageInfo {
 			cache_reads: UsageUnit::default(),
 			modified_reads: UsageUnit::default(),
 			memory: 0,
+			#[cfg(feature = "std")]
 			started: Instant::now(),
+			#[cfg(feature = "std")]
 			span: Default::default(),
 		}
 	}