Promote API version 2 to supported (#4803)

* Promote API version 2 to supported

* Switch command line to API version 1

* Fix LedgerRequestRPC test

* Remove obsolete tx_account method

This method is not implemented, the only parts which are removed are related to command-line parsing

* Fix RPCCall test

* Reduce diff size, small test improvements

* Minor fixes

* Support for the mold linker

* [fold] handle case where both mold and gold are installed

* [fold] Use first non-default linker

* Fix TransactionEntry_test

* Fix AccountTx_test

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Co-authored-by: seelabs <scott.determan@yahoo.com>

src/test/jtx/impl/Env.cpp

@@ -460,15 +460,11 @@ Env::st(JTx const& jt)
 
 Json::Value
 Env::do_rpc(
+    unsigned apiVersion,
     std::vector<std::string> const& args,
     std::unordered_map<std::string, std::string> const& headers)
 {
-    return rpcClient(
-               args,
-               app().config(),
-               app().logs(),
-               RPC::apiMaximumSupportedVersion,
-               headers)
+    return rpcClient(args, app().config(), app().logs(), apiVersion, headers)
         .second;
 }