daemon/proxyv2: fix client TCP/TLS + merge state structs

Firstly, this adds a missing assignment of comm->proxy, which would cause the resolver not to know that a client asked via TCP/TLS, if the proxy also asked via TCP/TLS.

Secondly, it merges struct pl_proxyv2_sess_data and struct pl_proxyv2_iter_data into a single struct pl_proxyv2_state, since they were practically the same. And it adds a bit of documentation to the struct.

daemon/proxyv2.test/kresd_config.j2

@@ -2,7 +2,6 @@
 {% raw %}
 modules.load('view < policy')
 view:addr("127.127.0.0", policy.suffix(policy.DENY_MSG("addr 127.127.0.0 matched com"),{"\3com\0"}))
--- policy.add(policy.all(policy.FORWARD('1.2.3.4')))
 
 -- make sure DNSSEC is turned off for tests
 trust_anchors.remove('.')