rfc43: update job-list.list to streaming RPC

Problem: job-list.list RPC currently responds to requests with
a single large array of jobs.  This response can be extremely
large, and could lead to head-of-line blocking.

Update the job-list.list RPC to support streaming RPCs.  This will
allow jobs to be streamed back to the caller in smaller increments.

Author: chu11

spec_43.rst

@@ -272,7 +272,7 @@ List
 
 The :program:`job-list.list` RPC fetches a list of jobs.
 
-The list of jobs shall be filtered in the following order.
+The list of jobs SHALL be filtered in the following order.
 
 - pending jobs
 - running jobs
@@ -282,6 +282,12 @@ Pending jobs are returned ordered by priority (higher priority first),
 running jobs ordered by start time (most recent first), and inactive
 jobs ordered by completion (most recently finished first)
 
+The RPC request SHOULD specify FLUX_MSGFLAG_STREAMING as described in
+RFC 6 so that the server has the opportunity to manage response
+message size for large query results.  When that flag is specified,
+responses SHALL be split over multiple messages, terminated with error
+61, "No data available" (ENODATA).
+
 The RPC payloads are defined as follows:
 
 .. object:: job-info.lookup request
@@ -313,7 +319,8 @@ The RPC payloads are defined as follows:
 
 .. object:: job-info.lookup response
 
-  The response SHALL consist of a JSON object with the following keys:
+  Each non-error response SHALL consist of a JSON object with the
+  following keys:
 
   .. object:: jobs