Introduce BlockExecutionWeight and ExtrinsicBaseWeight

[shawntabrizi]

This PR introduces the following concepts:

• Every extrinsic has some base weight for existing in a block. For example, Reading/Writing from the sender account in storage, signature verification, etc...

• Every block has some base weight independent of the included extrinsics.

To account for this, we make the following changes:

New System Traits

We introduce 2 new system configuration traits to account for all weights in the block execution process.

1. BlockExecutionWeight: A fixed value that takes into account any overhead introduced by simply executing a block, not including the execution of the transactions themselves.

	/// Actually execute all transitions for `block`.
	pub fn execute_block(block: Block) {
		Self::initialize_block(block.header());

		// any initial checks
		Self::initial_checks(&block);

		let batching_safeguard = sp_runtime::SignatureBatching::start();
		// execute extrinsics
		let (header, extrinsics) = block.deconstruct();
		Self::execute_extrinsics_with_book_keeping(extrinsics, *header.number());
		if !sp_runtime::SignatureBatching::verify(batching_safeguard) {
			panic!("Signature verification failed.");
		}

		// any final checks
		Self::final_checks(&header);
	}

So the stuff above minus execute_extrinsics_with_book_keeping

2. ExtrinsicBaseWeight: A fixed value that takes into account any overhead introduced by simply including an extrinsic in a block. Measured by executing many no-op extrinsics and deriving the individual cost of one such extrinsic.

These two weights will automatically be included through the block execution process when defined in the runtime.

We also replace the notion of TransactionBaseFee with ExtrinsicBaseWeight * WeightToFee.

New Weight Logic

Before this PR (and the larger goal of updating all extrinsic weights), all weights were constant. As a result, we assumed that no weight would be too big for a single block.

Now that extrinsic weights could be represented by formulas, and the input to an extrinsic could be beyond the capabilities of the blockchain. So we introduce the following new behavior:

• Any extrinsic whose weight would push the weight of a block past its limit is discarded with the error ExhaustedResources.
• There is an exception to this rule with DispatchClass::Mandatory, which will be allowed in a block no matter what. This may cause the weight of a block to be larger than MaximumBlockWeight.

This weight pipeline needs to take into account the new traits we defined, so to make it a bit more ergonomic to define weights, we also introduce a new System function max_extrinsic_weight, which takes a DispatchClass and returns the max weight allowed for an extrinsic in a block. Only one such extrinsic like this could exist in a block.

This PR also removed MINIMUM_WEIGHT, since that concept is basically replaced with ExtrinsicBaseWeight now.

[gnunicorn]

bot merge

[shawntabrizi]

bot merge

[ghost]

Cannot merge; please ensure the pull request is mergeable and has approval from the project owner or at least 2 core devs.

[ghost]

bot merge cancel

[sjeohp-zz]

bot merge

[ghost]

bot merge complete