rpc/graphql: implement transaction resolver, fix Long scalar and pre-Byzantium status (#20916)

### New implementations
- `transaction(hash)`: implemented transaction lookup by hash (was
panicking)
- `block(hash)`: implemented block lookup by hash (was unimplemented)
- `block.transactionAt(index)`: implemented with proper bounds checking
(was panicking)
  ### Bug fixes                                                         
- `transaction.type`: changed schema from `Int` to `Long` so
EIP-1559/EIP-4844
transactions return `"0x2"` / `"0x3"` (hex) instead of `2` / `3`
(decimal),
matching the GraphQL spec
- `transaction.status`: pre-Byzantium blocks now correctly return
`"0x0"` instead
of `null` (pre-Byzantium receipts carry `PostState` instead of `Status`)
- `transaction.gas`, `transaction.maxFeePerGas`,
`transaction.maxPriorityFeePerGas`,
`transaction.accessList`: fields were missing from the receipt map and
are now
populated correctly
                                                                        
### Hive simulator fix
- Added `HIVE_CANCUN_TIMESTAMP` to the client environment map in the
GraphQL hive
simulator. Without it, Erigon rejected Cancun blocks during chain
import,
truncating the canonical chain at block 29 and causing ~10 tests to fail
(withdrawals, Shanghai/Cancun block queries, block range queries).
## Tests
- Added unit tests for the new `Long` scalar (marshal/unmarshal)
- Added unit tests for nil guards in the `convertData` helpers
- Added unit tests for `transactionAt` bounds checking
- Added unit tests for `transaction` invalid hash error handling

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>
Co-authored-by: Alex Sharov <AskAlexSharov@gmail.com>

Author: 3 people

cmd/rpcdaemon/graphql/gqlgen.yml

@@ -60,7 +60,7 @@ models:
       - github.com/99designs/gqlgen/graphql.Int32
   Long:
     model:
-      - github.com/99designs/gqlgen/graphql.Uint64
+      - github.com/erigontech/erigon/cmd/rpcdaemon/graphql/graph/scalar.Uint64
   BigInt:
     model:
       - github.com/99designs/gqlgen/graphql.String
@@ -77,13 +77,17 @@ models:
     model:
       - github.com/99designs/gqlgen/graphql.String
       - github.com/99designs/gqlgen/graphql.Uint64
-#  Block:
-#    fields:
-#      logs:
-#        resolver: true # force a resolver to be generated
-#      ommers:
-#        resolver: true # force a resolver to be generated
-#      transactions:
-#        resolver: true # force a resolver to be generated
+  Block:
+    fields:
+      transactionAt:
+        resolver: true
+      account:
+        resolver: true
+  Transaction:
+    fields:
+      from:
+        resolver: true
+      to:
+        resolver: true
 
 omit_getters: true