Properly avoid advisory Yugabyte lock erorrs

The `try_lock` method was not properly checking for Yugabyte before
attempting to acquire an adivosory lock. Likely it used to be a warning,
but now is an error that cannot be avoided. So have `try_lock` check for
Yugabyte before attempting to take an advisory lock. This requires
fetching the database handle, first, as the database is not identified
until it connects. So also fetch the handle earlier in `wait_lock`, just
to be careful.

While at it, on Yugabyte set the
`yb_silence_advisory_locks_not_supported_error` GUC to avoid the whole
issue whenever possible.

Fixes #841.

Changes

@@ -10,6 +10,11 @@ Revision history for Perl extension App::Sqitch
        exception objects rather than strings, for more consistent error
        handling throughout.
      - Removed duplicate DBI error handling code from engines and tests.
+     - Fixed an order of operation issue that prevented Sqitch from detecting
+       Yugabyte before attempting to create an advisory lock, which results in
+       an error for more recent Yugabyte releases. Also set a GUC to avoid the
+       advisory lock errors altogether. Thanks to Stefano Ricciardi for the
+       report and to Franck Pachot for the GUC suggestion (#841).
 
 1.4.1  2024-02-04T16:35:32Z
      - Removed the quoting of the role and warehouse identifiers that was

lib/App/Sqitch/Engine/pg.pm

@@ -144,7 +144,11 @@ has dbh => (
                     my $v = $dbh->selectcol_arrayref(
                         q{SELECT split_part(version(), ' ', 2)}
                     )->[0] // '';
-                    $self->_provider('yugabyte') if $v =~ /-YB-/;
+                    if ($v =~ /-YB-/) {
+                        $dbh->do('SET yb_silence_advisory_locks_not_supported_error = true');
+                        $self->_provider('yugabyte')
+                    }
+
                     return;
                 },
             },
@@ -287,7 +291,11 @@ sub begin_work {
 
 # Override to try to acquire a lock on a constant number without waiting.
 sub try_lock {
-    shift->dbh->selectcol_arrayref(
+    my $self = shift;
+    # _provider not set till we fetch dbh.
+    my $dbh = $self->dbh;
+    return 1 if $self->_provider ne 'postgres';
+    $dbh->selectcol_arrayref(
         'SELECT pg_try_advisory_lock(75474063)'
     )->[0]
 }
@@ -296,6 +304,7 @@ sub try_lock {
 # until timeout.
 sub wait_lock {
     my $self = shift;
+    my $dbh = $self->dbh;
 
     # Yugabyte does not support advisory locks.
     # https://github.com/yugabyte/yugabyte-db/issues/3642
@@ -304,7 +313,6 @@ sub wait_lock {
     return 1 if $self->_provider ne 'postgres';
 
     # Asynchronously request a lock with an indefinite wait.
-    my $dbh = $self->dbh;
     $dbh->do(
         'SELECT pg_advisory_lock(75474063)',
         { pg_async => DBD::Pg::PG_ASYNC() },