libzfs: migrate single-use libzfs_set_pipe_max() to libzfs_core

Notably, this also means that the pipe is expanded before each
dataset is received, so updates to /p/s/f/pipe-max-size are reflected
for each new dataset

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Rich Ercolani <rincebrain@gmail.com>
Reviewed-by: Paul Dagnelie <pcd@delphix.com>
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Closes #13133

lib/libzfs/libzfs_impl.h

@@ -257,7 +257,6 @@ extern int libzfs_load_module(void);
 extern int zpool_relabel_disk(libzfs_handle_t *hdl, const char *path,
     const char *msg);
 extern int find_shares_object(differ_info_t *di);
-extern void libzfs_set_pipe_max(int infd);
 extern void zfs_commit_proto(const zfs_share_proto_t *);
 
 #ifdef	__cplusplus