gRPC support for account_tx and tx

- Add support for all transaction types and ledger object types to gRPC
  implementation of tx and account_tx.

- Create common handlers for tx and account_tx.

- Remove mutex and abort() from gRPC server. JobQueue is stopped before
  gRPC server, with all coroutines executed to completion, so no need for
  synchronization.

src/test/jtx.h

@@ -24,6 +24,7 @@
 
 #include <ripple/json/to_string.h>
 #include <test/jtx/Account.h>
+#include <test/jtx/account_txn_id.h>
 #include <test/jtx/acctdelete.h>
 #include <test/jtx/amount.h>
 #include <test/jtx/balance.h>
@@ -34,8 +35,10 @@
 #include <test/jtx/Env_ss.h>
 #include <test/jtx/fee.h>
 #include <test/jtx/flags.h>
+#include <test/jtx/invoice_id.h>
 #include <test/jtx/jtx_json.h>
 #include <test/jtx/JTx.h>
+#include <test/jtx/last_ledger_sequence.h>
 #include <test/jtx/memo.h>
 #include <test/jtx/multisign.h>
 #include <test/jtx/noop.h>