CLEANUP: conn_stream: tree-wide rename to stconn (stream connector)

This renames the "struct conn_stream" to "struct stconn" and updates
the descriptions in all comments (and the rare help descriptions) to
"stream connector" or "connector". This touches a lot of files but
the change is minimal. The local variables were not even renamed, so
there's still a lot of "cs" everywhere.
diff --git a/src/ssl_sock.c b/src/ssl_sock.c
index b7c5260..1c614d2 100644
--- a/src/ssl_sock.c
+++ b/src/ssl_sock.c
@@ -7259,7 +7259,7 @@
 static int cli_io_handler_tlskeys_files(struct appctx *appctx)
 {
 	struct show_keys_ctx *ctx = appctx->svcctx;
-	struct conn_stream *cs = appctx_cs(appctx);
+	struct stconn *cs = appctx_cs(appctx);
 
 	switch (ctx->state) {
 	case SHOW_KEYS_INIT:
@@ -7538,7 +7538,7 @@
 	struct buffer *trash = alloc_trash_chunk();
 	struct buffer *tmp = NULL;
 	struct ebmb_node *node;
-	struct conn_stream *cs = appctx_cs(appctx);
+	struct stconn *cs = appctx_cs(appctx);
 	struct certificate_ocsp *ocsp = NULL;
 	BIO *bio = NULL;
 	int write = -1;
@@ -7674,7 +7674,7 @@
 static int cli_io_handler_show_providers(struct appctx *appctx)
 {
 	struct buffer *trash = get_trash_chunk();
-	struct conn_stream *cs = appctx_cs(appctx);
+	struct stconn *cs = appctx_cs(appctx);
 	struct list provider_names;
 	struct provider_name *name;
 
@@ -7805,7 +7805,7 @@
 {
 	struct buffer *trash = alloc_trash_chunk();
 	struct certificate_ocsp *ocsp = appctx->svcctx;
-	struct conn_stream *cs = appctx_cs(appctx);
+	struct stconn *cs = appctx_cs(appctx);
 
 	if (trash == NULL)
 		return 1;
@@ -7882,7 +7882,7 @@
                                        struct session *sess, struct stream *s, int flags)
 {
 	struct connection *conn;
-	struct conn_stream *cs;
+	struct stconn *cs;
 
 	conn = objt_conn(sess->origin);
 	cs = s->csf;