Add grandpa telemetry (+ other minor improvements) (#1997)

* Support skipping the interactive purge prompt

Skip it via `cargo run -- purge-chain -y`.

* Fix typos

* Add Grandpa telemetry

* Address comments

* Revert unnecessary version bump

* Version bump to make CI run

* Remove unnecessary cast

* Do not bump version

substrate/core/test-runtime/src/lib.rs

@@ -214,7 +214,7 @@ cfg_if! {
 			pub trait TestAPI {
 				/// Return the balance of the given account id.
 				fn balance_of(id: AccountId) -> u64;
-				/// A benchmkark function that adds one to the given value and returns the result.
+				/// A benchmark function that adds one to the given value and returns the result.
 				fn benchmark_add_one(val: &u64) -> u64;
 				/// A benchmark function that adds one to each value in the given vector and returns the
 				/// result.
@@ -239,7 +239,7 @@ cfg_if! {
 			pub trait TestAPI {
 				/// Return the balance of the given account id.
 				fn balance_of(id: AccountId) -> u64;
-				/// A benchmkark function that adds one to the given value and returns the result.
+				/// A benchmark function that adds one to the given value and returns the result.
 				fn benchmark_add_one(val: &u64) -> u64;
 				/// A benchmark function that adds one to each value in the given vector and returns the
 				/// result.

substrate/core/test-runtime/src/system.rs

@@ -52,7 +52,7 @@ pub fn nonce_of(who: AccountId) -> u64 {
 	storage::get_or(&who.to_keyed_vec(NONCE_OF), 0)
 }
 
-/// Get authorities ar given block.
+/// Get authorities at given block.
 pub fn authorities() -> Vec<AuthorityId> {
 	let len: u32 = storage::unhashed::get(well_known_keys::AUTHORITY_COUNT)
 		.expect("There are always authorities in test-runtime");