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/frame/system/src/limits.rs

@@ -378,7 +378,7 @@ impl BlockWeightsBuilder {
 	/// class, based on the allowance.
 	///
 	/// This is to make sure that extrinsics don't stay forever in the pool,
-	/// because they could seamingly fit the block (since they are below `max_block`),
+	/// because they could seemingly fit the block (since they are below `max_block`),
 	/// but the cost of calling `on_initialize` always prevents them from being included.
 	pub fn avg_block_initialization(mut self, init_cost: Perbill) -> Self {
 		self.init_cost = Some(init_cost);

substrate/frame/system/src/offchain.rs

@@ -22,7 +22,7 @@
 //! This module provides transaction related helpers to:
 //! - Submit a raw unsigned transaction
 //! - Submit an unsigned transaction with a signed payload
-//! - Submit a signed transction.
+//! - Submit a signed transaction.
 //!
 //! ## Usage
 //!
@@ -384,7 +384,7 @@ where
 ///
 /// // runtime-specific public key
 /// type Public = MultiSigner: From<sr25519::Public>;
-/// type Signature = MulitSignature: From<sr25519::Signature>;
+/// type Signature = MultiSignature: From<sr25519::Signature>;
 /// ```
 // TODO [#5662] Potentially use `IsWrappedBy` types, or find some other way to make it easy to
 // obtain unwrapped crypto (and wrap it back).
@@ -444,7 +444,7 @@ pub trait SigningTypes: crate::Config {
 	/// A public key that is capable of identifying `AccountId`s.
 	///
 	/// Usually that's either a raw crypto public key (e.g. `sr25519::Public`) or
-	/// an aggregate type for multiple crypto public keys, like `MulitSigner`.
+	/// an aggregate type for multiple crypto public keys, like `MultiSigner`.
 	type Public: Clone
 		+ PartialEq
 		+ IdentifyAccount<AccountId = Self::AccountId>