feat: compute valid blockhashes for block history

[bmuddha]

In current implementation of the validator, we make up the blockhashes, i.e. they are not related to the ledger, and are produced by a separate validator logic. In order to have a verifiable replication, we need proper blockhashes, i.e. blockhashes which are reflect tha blockchain history.

Need to investigate a streaming blockhash computation, tied to the scheduler. The main concern is to do it in least invasive fashion and without introducing any race conditions related to slot transitions, where different threads might get out of sync on slot boundaries.

useful links:

magicblock-validator/magicblock-processor/src/scheduler/mod.rs

Line 193 in 9edc6c4

fn transition_to_new_slot(&self) {

magicblock-validator/magicblock-processor/src/executor/mod.rs

Line 157 in 9edc6c4

_ = block_updated.recv() => {

magicblock-validator/magicblock-processor/src/executor/mod.rs

Line 169 in 9edc6c4

fn transition_to_new_slot(&mut self) {

[bmuddha]

Settled on the preliminary design. The idea is to move the slot ticker to the scheduler, into the select loop

magicblock-validator/magicblock-processor/src/scheduler/mod.rs

Line 141 in 190bd7a

tokio::select! {

whenever slot ticks, we take the running blockhash value and persist it to the ledger. Update the local slot, and communicate the the blockhash/blocktime to the executors.
Thus neither the scheduler nor executors need to listen to the block updates.

The other part of design is to use the slot included with the transaction to adjust sysvar cache of the executor which picked up the transaction (optimized way is to only touch sysvars if the slot has changed).

magicblock-validator/magicblock-processor/src/scheduler/mod.rs

Line 221 in 190bd7a

let txn = IndexedTransaction { slot, index, txn };

Every time the executor receives the transaction, it should update slot related state if necessary

magicblock-validator/magicblock-processor/src/executor/mod.rs

Line 198 in 190bd7a

fn set_sysvars(&self, block: &LatestBlockInner) {