feat: improve visibility for runtime performance

tracing::span records how long it took to run a block of code and prints
this into into log.

See

https://github.com/near/nearcore/blob/ff01c544ce2675fadbf0284af52b356a383b27a8/docs/architecture.md#runtimenear-vm-runner

for the info on the tracing infra

runtime/runtime/Cargo.toml

@@ -9,6 +9,7 @@ byteorder = "1.2"
 serde = { version = "1", features = ["derive"] }
 serde_json = "1.0"
 log = "0.4"
+tracing = "0.1.13"
 rand = "0.7"
 lazy_static = "1.4"
 num-rational = "0.3"

runtime/runtime/src/lib.rs

@@ -217,7 +217,10 @@ impl Runtime {
         signed_transaction: &SignedTransaction,
         stats: &mut ApplyStats,
     ) -> Result<(Receipt, ExecutionOutcomeWithId), RuntimeError> {
+        let _span =
+            tracing::debug_span!(target: "runtime", "Runtime::process_transaction").entered();
         near_metrics::inc_counter(&metrics::TRANSACTION_PROCESSED_TOTAL);
+
         match verify_and_charge_transaction(
             &apply_state.config,
             state_update,
@@ -817,6 +820,8 @@ impl Runtime {
         stats: &mut ApplyStats,
         epoch_info_provider: &dyn EpochInfoProvider,
     ) -> Result<Option<ExecutionOutcomeWithId>, RuntimeError> {
+        let _span = tracing::debug_span!(target: "runtime", "Runtime::process_receipt").entered();
+
         let account_id = &receipt.receiver_id;
         match receipt.receipt {
             ReceiptEnum::Data(ref data_receipt) => {
@@ -1156,9 +1161,12 @@ impl Runtime {
         epoch_info_provider: &dyn EpochInfoProvider,
         states_to_patch: Option<Vec<StateRecord>>,
     ) -> Result<ApplyResult, RuntimeError> {
+        let _span = tracing::debug_span!(target: "runtime", "Runtime::apply").entered();
+
         if states_to_patch.is_some() && !cfg!(feature = "sandbox") {
             panic!("Can only patch state in sandbox mode");
         }
+
         let trie = Rc::new(trie);
         let initial_state = TrieUpdate::new(trie.clone(), root);
         let mut state_update = TrieUpdate::new(trie.clone(), root);