Use setproctitle to report progress of zfs send

This allows parsing of zfs send progress by checking the process
title.
Doing so requires some changes to the send code in libzfs_sendrecv.c;
primarily these changes move some of the accounting around, to allow
for the code to be verbose as normal, or set the process title. Unlike
BSD, setproctitle() isn't standard in Linux; thus, borrowed it from
libbsd with slight modifications.

Authored-by: Sean Eric Fagan <sef@FreeBSD.org>
Co-authored-by: Ryan Moeller <ryan@iXsystems.com>
Co-authored-by: Ameer Hamza <ahamza@ixsystems.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Ryan Moeller <ryan@iXsystems.com>
Signed-off-by: Ameer Hamza <ahamza@ixsystems.com>
Closes #14376

include/libzfs.h

@@ -693,6 +693,9 @@ typedef struct sendflags {
 	/* show progress (ie. -v) */
 	boolean_t progress;
 
+	/* show progress as process title (ie. -V) */
+	boolean_t progressastitle;
+
 	/* large blocks (>128K) are permitted */
 	boolean_t largeblock;
 

include/libzutil.h

@@ -167,6 +167,14 @@ void color_start(const char *color);
 void color_end(void);
 int printf_color(const char *color, char *format, ...);
 
+#ifdef __linux__
+_LIBZUTIL_H void zfs_setproctitle_init(int argc, char *argv[], char *envp[]);
+_LIBZUTIL_H void zfs_setproctitle(const char *fmt, ...);
+#else
+#define	zfs_setproctitle(fmt, ...)	setproctitle(fmt, ##__VA_ARGS__)
+#define	zfs_setproctitle_init(x, y, z)	((void)0)
+#endif
+
 /*
  * These functions are used by the ZFS libraries and cmd/zpool code, but are
  * not exported in the ABI.