add get_interchain: trace a transaction/block to validator blocks + interchain anchors

New transaction.get_interchain and block.get_interchain call the prime-node
/api/v1/{transaction,block}/{id}/interchain endpoints, returning an
InterchainTrace {block_id, validator_blocks, interchain_transactions}. Adds
VerificationBlock / InterchainTransaction / InterchainTrace dataclasses with
from_dict, exports them, and a from_dict test.

prime_sdk/transaction.py

@@ -2,6 +2,7 @@
 
 from .client import CONTENT_TYPE_JSON, Client
 from .models import (
+    InterchainTrace,
     ListTransactionsResponse,
     Transaction,
     TransactionBulkRequest,
@@ -39,5 +40,14 @@ class TransactionClient:
     def get(self, transaction_id: str) -> Transaction:
         return self._client.get(f"/api/v1/transaction/{transaction_id}", Transaction)
 
+    def get_interchain(self, transaction_id: str) -> InterchainTrace:
+        """Trace a transaction to the validator (verification) blocks that
+        validated its prime block and the public-chain interchain anchors those
+        validator blocks were bundled into. If the transaction is still pending
+        (not yet in a block) the trace's lists are empty."""
+        return self._client.get(
+            f"/api/v1/transaction/{transaction_id}/interchain", InterchainTrace
+        )
+
     def list(self) -> ListTransactionsResponse:
         return self._client.get("/api/v1/transaction/", ListTransactionsResponse)