progress: estimate actual data sizes for progress report

Replace pointers in the "done" and "total" columns with estimated data
sizes for each size tier.  The estimation is based on statistics
collected from extents scanned during the current bees run.

Move the total size for the entire filesystem up to the heading.

Report the _completed_ position (i.e. the one that would be saved in
`beescrawl.dat`), not the _queued_ position (i.e. the one where the
next Task would be created in memory).

At the end of the data, the crawl pointer ends up at some random point
in the filesystem just after the newest extent, so the progress gets to
99.7% and then goes to some random value like 47% or 3%, not to 100%.
Report "deferred" in the "done" column when the crawler is waiting for
the next transid, and "finished" in the "%done" column when the crawler
has reached the end of the data.  Suppress the ETA when finished.  This
makes it clear that there's no further work to do for these crawlers.

Signed-off-by: Zygo Blaxell <bees@furryterror.org>

src/bees.h

@@ -533,6 +533,8 @@ public:
 	BeesCrawlState get_state_end() const;
 	void set_state(const BeesCrawlState &bcs);
 	void deferred(bool def_setting);
+	bool deferred() const;
+	bool finished() const;
 };
 
 class BeesScanMode;