vacuumdb: Add option --analyze-in-stages

Add vacuumdb option --analyze-in-stages which runs ANALYZE three times
with different configuration settings, adopting the logic from the
analyze_new_cluster.sh script that pg_upgrade generates.  That way,
users of pg_dump/pg_restore can also use that functionality.

Change pg_upgrade to create the script so that it calls vacuumdb instead
of implementing the logic itself.

src/bin/scripts/t/102_vacuumdb_stages.pl

@@ -0,0 +1,16 @@
+use strict;
+use warnings;
+use TestLib;
+use Test::More tests => 1;
+
+my $tempdir = tempdir;
+start_test_server $tempdir;
+
+issues_sql_like(['vacuumdb', '--analyze-in-stages', 'postgres'],
+				qr/.*statement:\ SET\ default_statistics_target=1;\ SET\ vacuum_cost_delay=0;
+                   .*statement:\ ANALYZE.*
+                   .*statement:\ SET\ default_statistics_target=10;\ RESET\ vacuum_cost_delay;
+                   .*statement:\ ANALYZE.*
+                   .*statement:\ RESET\ default_statistics_target;
+                   .*statement:\ ANALYZE/sx,
+				'analyze three times');