feat(sequencer): implement basic app side mempool with nonce ordering (…

…#1000)

## Summary
implement a basic app side mempool with nonce ordering. 

the mempool works as follows:
- when a tx passes `check_tx`, it's inserted into the mempool. if a tx
fails `check_tx` it's removed from the mempool (if it was in it already)
- during `prepare_proposal`, txs passed in from cometbft are ignored,
and txs are popped from the app's mempool instead.
- after a block is finalized, any included txs are removed from the
mempool, and the priorities of the txs remaining are updated.
- txs in the mempool are ordered by nonce, specifically the differential
between the tx nonce and the current account nonce. the lower the
differential, the higher the priority. for example, a tx with nonce 7
sent from an account with nonce 7 is a higher priority than a tx with
nonce 1 sent from an account with nonce 0.

question (maybe for a follow up): there is no reason for a non-validator
node to have the app-side mempool, as it doesn't gossip. should we make
a config flag to enable/disable it?

## Background
- cometbft mempool is too opaque, doesn't know about app-specific
ordering, should only be used for tx gossip
- will help with the sequencer api (can return pending nonce for an
account)
- can use for fee-based ordering or tx expiry time in the future

## Changes
- implementation of a basic nonce-ordered mempool
- update `App` to use this mempool (see summary for how it works)
- updated `App` to have separate functions for executing txs in prepare
vs process proposal, as the functionality of the two was diverging too
much
- update the `mempool` service to also use the mempool in `check_tx`

## Testing
unit tests

## Related Issues

closes #856

crates/astria-core/src/protocol/transaction/v1alpha1/mod.rs

@@ -187,6 +187,11 @@ impl SignedTransaction {
     pub fn unsigned_transaction(&self) -> &UnsignedTransaction {
         &self.transaction
     }
+
+    #[must_use]
+    pub fn nonce(&self) -> u32 {
+        self.transaction.params.nonce
+    }
 }
 
 #[derive(Clone, Debug)]

crates/astria-sequencer/Cargo.toml

@@ -27,6 +27,7 @@ telemetry = { package = "astria-telemetry", path = "../astria-telemetry", featur
 anyhow = "1"
 borsh = { version = "1", features = ["derive"] }
 matchit = "0.7.2"
+priority-queue = "2.0.2"
 tower = "0.4"
 tower-abci = "0.12.0"
 tower-actor = "0.1.0"