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.~~

substrate/primitives/blockchain/src/backend.rs

@@ -187,7 +187,7 @@ pub trait Backend<Block: BlockT>:
 	/// a block with the given `base_hash`.
 	///
 	/// The search space is always limited to blocks which are in the finalized
-	/// chain or descendents of it.
+	/// chain or descendants of it.
 	///
 	/// Returns `Ok(None)` if `base_hash` is not found in search space.
 	// TODO: document time complexity of this, see [#1444](https://github.com/paritytech/substrate/issues/1444)

substrate/primitives/blockchain/src/error.rs

@@ -34,7 +34,7 @@ pub enum ApplyExtrinsicFailed {
 	/// The transaction cannot be included into the current block.
 	///
 	/// This doesn't necessary mean that the transaction itself is invalid, but it might be just
-	/// unappliable onto the current block.
+	/// unapplicable onto the current block.
 	#[error("Extrinsic is not valid: {0:?}")]
 	Validity(#[from] TransactionValidityError),
 

substrate/primitives/blockchain/src/header_metadata.rs

@@ -178,7 +178,7 @@ pub struct TreeRoute<Block: BlockT> {
 impl<Block: BlockT> TreeRoute<Block> {
 	/// Creates a new `TreeRoute`.
 	///
-	/// To preserve the structure safety invariats it is required that `pivot < route.len()`.
+	/// To preserve the structure safety invariants it is required that `pivot < route.len()`.
 	pub fn new(route: Vec<HashAndNumber<Block>>, pivot: usize) -> Result<Self, String> {
 		if pivot < route.len() {
 			Ok(TreeRoute { route, pivot })
@@ -212,7 +212,7 @@ impl<Block: BlockT> TreeRoute<Block> {
 		)
 	}
 
-	/// Get a slice of enacted blocks (descendents of the common ancestor)
+	/// Get a slice of enacted blocks (descendants of the common ancestor)
 	pub fn enacted(&self) -> &[HashAndNumber<Block>] {
 		&self.route[self.pivot + 1..]
 	}