Implement receipt value check

[aasseman]

Problem statement
TAP Agent does not currently check that the receipt values are correct w.r.t the query and Agora model.

Expectation proposal
Computing a query's price w.r.t. an Agora model is fairly easy on principle, as the canonical Agora implementation already is a Rust library: https://github.com/graphprotocol/agora.

However:

• Indexers can change their Agora models at any time.
• Gateways poll the indexer's models at a regular interval (~30sec).
• The indexer is not informed of which model was used for a particular query (would have to guess by testing its most recent model versions).
• There is no standard currently as to how long a gateway is authorized to use an obsolete model.

Additional context

indexer-rs/tap-agent/src/tap/sender_allocation_relationship.rs

Lines 96 to 103 in 1178c63

	let required_checks = vec![
	ReceiptCheck::CheckUnique,
	ReceiptCheck::CheckAllocationId,
	ReceiptCheck::CheckTimestamp,
	// ReceiptCheck::CheckValue,
	ReceiptCheck::CheckSignature,
	ReceiptCheck::CheckAndReserveEscrow,
	];