Fix spelling mistakes across the whole repository (#3808)

**Update:** Pushed additional changes based on the review comments.

**This pull request fixes various spelling mistakes in this
repository.**

Most of the changes are contained in the first **3** commits:

- `Fix spelling mistakes in comments and docs`

- `Fix spelling mistakes in test names`

- `Fix spelling mistakes in error messages, panic messages, logs and
tracing`

Other source code spelling mistakes are separated into individual
commits for easier reviewing:

- `Fix the spelling of 'authority'`

- `Fix the spelling of 'REASONABLE_HEADERS_IN_JUSTIFICATION_ANCESTRY'`

- `Fix the spelling of 'prev_enqueud_messages'`

- `Fix the spelling of 'endpoint'`

- `Fix the spelling of 'children'`

- `Fix the spelling of 'PenpalSiblingSovereignAccount'`

- `Fix the spelling of 'PenpalSudoAccount'`

- `Fix the spelling of 'insufficient'`

- `Fix the spelling of 'PalletXcmExtrinsicsBenchmark'`

- `Fix the spelling of 'subtracted'`

- `Fix the spelling of 'CandidatePendingAvailability'`

- `Fix the spelling of 'exclusive'`

- `Fix the spelling of 'until'`

- `Fix the spelling of 'discriminator'`

- `Fix the spelling of 'nonexistent'`

- `Fix the spelling of 'subsystem'`

- `Fix the spelling of 'indices'`

- `Fix the spelling of 'committed'`

- `Fix the spelling of 'topology'`

- `Fix the spelling of 'response'`

- `Fix the spelling of 'beneficiary'`

- `Fix the spelling of 'formatted'`

- `Fix the spelling of 'UNKNOWN_PROOF_REQUEST'`

- `Fix the spelling of 'succeeded'`

- `Fix the spelling of 'reopened'`

- `Fix the spelling of 'proposer'`

- `Fix the spelling of 'InstantiationNonce'`

- `Fix the spelling of 'depositor'`

- `Fix the spelling of 'expiration'`

- `Fix the spelling of 'phantom'`

- `Fix the spelling of 'AggregatedKeyValue'`

- `Fix the spelling of 'randomness'`

- `Fix the spelling of 'defendant'`

- `Fix the spelling of 'AquaticMammal'`

- `Fix the spelling of 'transactions'`

- `Fix the spelling of 'PassingTracingSubscriber'`

- `Fix the spelling of 'TxSignaturePayload'`

- `Fix the spelling of 'versioning'`

- `Fix the spelling of 'descendant'`

- `Fix the spelling of 'overridden'`

- `Fix the spelling of 'network'`

Let me know if this structure is adequate.

**Note:** The usage of the words `Merkle`, `Merkelize`, `Merklization`,
`Merkelization`, `Merkleization`, is somewhat inconsistent but I left it
as it is.

~~**Note:** In some places the term `Receival` is used to refer to
message reception, IMO `Reception` is the correct word here, but I left
it as it is.~~

~~**Note:** In some places the term `Overlayed` is used instead of the
more acceptable version `Overlaid` but I also left it as it is.~~

~~**Note:** In some places the term `Applyable` is used instead of the
correct version `Applicable` but I also left it as it is.~~

**Note:** Some usage of British vs American english e.g. `judgement` vs
`judgment`, `initialise` vs `initialize`, `optimise` vs `optimize` etc.
are both present in different places, but I suppose that's
understandable given the number of contributors.

~~**Note:** There is a spelling mistake in `.github/CODEOWNERS` but it
triggers errors in CI when I make changes to it, so I left it as it
is.~~

polkadot/node/core/runtime-api/src/tests.rs

@@ -299,12 +299,12 @@ impl RuntimeApiSubsystemClient for MockSubsystemClient {
 #[test]
 fn requests_authorities() {
 	let (ctx, mut ctx_handle) = make_subsystem_context(TaskExecutor::new());
-	let substem_client = Arc::new(MockSubsystemClient::default());
+	let subsystem_client = Arc::new(MockSubsystemClient::default());
 	let relay_parent = [1; 32].into();
 	let spawner = sp_core::testing::TaskExecutor::new();
 
 	let subsystem =
-		RuntimeApiSubsystem::new(substem_client.clone(), Metrics(None), SpawnGlue(spawner));
+		RuntimeApiSubsystem::new(subsystem_client.clone(), Metrics(None), SpawnGlue(spawner));
 	let subsystem_task = run(ctx, subsystem).map(|x| x.unwrap());
 	let test_task = async move {
 		let (tx, rx) = oneshot::channel();
@@ -315,7 +315,7 @@ fn requests_authorities() {
 			})
 			.await;
 
-		assert_eq!(rx.await.unwrap().unwrap(), substem_client.authorities);
+		assert_eq!(rx.await.unwrap().unwrap(), subsystem_client.authorities);
 
 		ctx_handle.send(FromOrchestra::Signal(OverseerSignal::Conclude)).await;
 	};
@@ -1042,7 +1042,7 @@ fn requests_submit_pvf_check_statement() {
 		let _ = rx.await.unwrap().unwrap();
 
 		assert_eq!(
-			&*subsystem_client.submitted_pvf_check_statement.lock().expect("poisened mutex"),
+			&*subsystem_client.submitted_pvf_check_statement.lock().expect("poisoned mutex"),
 			&[(stmt.clone(), sig.clone()), (stmt.clone(), sig.clone())]
 		);