refactor: extract state sync logic from Chain (#12833)

Main result: number of LoC in `chain/chain/src/chain.rs` goes from 4690
to 4125.

Please let me know if you want me to split this in multiple PRs. I can
do this but I'm very tempted to just go forward because there are no
functional changes...

### Biggest part (568+ lines)

It is moving state sync-related methods from `chain/chain/src/chain.rs`
to `chain/chain/src/state_sync/adapter.rs`. This is achieved by creating
`ChainStateSyncAdapter` which needs access to much less data than
`Chain`.

### Another change (156+ lines)

To achieve the previous one, I wanted to read chain data from
`ChainStoreAdapter`, not `ChainStore`. We are currently refactoring
`ChainStore` and I didn't want to create new instances of it. We can
allow read-only access to data which already exist in storage.

For this, in turn, I needed to make `get_chunk_clone_from_header`,
`get_block_header_on_chain_by_height` and
`get_incoming_receipts_for_shard` require only `ChainStoreAdapter`
access. I was able to move these to `chain/chain/src/store/utils.rs`
without changing logic.

Another bit of context: these methods previously required
`ChainStoreAccess` in order to be queried by `ChainStoreUpdate`. But as
@shreyan-gupta discovered, we don't actually need that, at least in
almost all places of the code. So it was natural to me to simplify
access to these functions already.

### Bonus

It was very easy to move `get_state_sync_info` to `ShardTracker` and
`StateRequestTracker` to new state sync folder - a nice example of
hiding implementation details.

Author: Longarithm

chain/chain/src/chain.rs

@@ -2,6 +2,7 @@ use crate::approval_verification::verify_approvals_and_threshold_orphan;
 use crate::block_processing_utils::BlockPreprocessInfo;
 use crate::chain::collect_receipts_from_response;
 use crate::metrics::{SHARD_LAYOUT_NUM_SHARDS, SHARD_LAYOUT_VERSION};
+use crate::store::utils::get_block_header_on_chain_by_height;
 use crate::store::{ChainStore, ChainStoreAccess, ChainStoreUpdate};
 use crate::types::{
     ApplyChunkBlockContext, ApplyChunkResult, ApplyChunkShardContext, RuntimeAdapter,
@@ -485,9 +486,13 @@ impl<'a> ChainUpdate<'a> {
             }
         };
 
-        let block_header = self
-            .chain_store_update
-            .get_block_header_on_chain_by_height(&sync_hash, chunk.height_included())?;
+        // Note that block headers are already synced and can be taken
+        // from store on disk.
+        let block_header = get_block_header_on_chain_by_height(
+            &self.chain_store_update.chain_store(),
+            &sync_hash,
+            chunk.height_included(),
+        )?;
 
         // Getting actual incoming receipts.
         let mut receipt_proof_responses: Vec<ReceiptProofResponse> = vec![];
@@ -625,8 +630,13 @@ impl<'a> ChainUpdate<'a> {
         let _span =
             tracing::debug_span!(target: "sync", "set_state_finalize_on_height", height, ?shard_id)
                 .entered();
-        let block_header_result =
-            self.chain_store_update.get_block_header_on_chain_by_height(&sync_hash, height);
+        // Note that block headers are already synced and can be taken
+        // from store on disk.
+        let block_header_result = get_block_header_on_chain_by_height(
+            &self.chain_store_update.chain_store(),
+            &sync_hash,
+            height,
+        );
         if let Err(_) = block_header_result {
             // No such height, go ahead.
             return Ok(true);

chain/chain/src/chain_update.rs

@@ -7,6 +7,7 @@ pub use doomslug::{Doomslug, DoomslugBlockProductionReadiness, DoomslugThreshold
 pub use lightclient::{create_light_client_block_view, get_epoch_block_producers_view};
 pub use near_chain_primitives::{self, Error};
 pub use near_primitives::receipt::ReceiptResult;
+pub use store::utils::{get_chunk_clone_from_header, get_incoming_receipts_for_shard};
 pub use store::{
     ChainStore, ChainStoreAccess, ChainStoreUpdate, LatestWitnessesInfo, MerkleProofAccess,
     ReceiptFilter,
@@ -32,7 +33,6 @@ pub mod orphan;
 pub mod resharding;
 pub mod runtime;
 pub mod signature_verification;
-mod state_request_tracker;
 pub mod state_snapshot_actor;
 mod state_sync;
 pub mod stateless_validation;