Bug 35921: Improve perfs of acqui-home.pl when there are many budgets

Bug 35921: Improve perfs of acqui-home.pl when there are many budgets

When there are a lot of budgets with the same owner, most of the time of
acqui-home.pl is spent loading the same patron over and over.

This patch makes sure each borrower is loaded only once.

Test plan:
0. Do not apply the patch yet
1. Create a thousand budgets with the following command (make sure the
   budget_owner_id is an existing borrowernumber):
       perl -MKoha::Database -e '
           my $schema = Koha::Database->schema;
           my $period = $schema->resultset("Aqbudgetperiod")->create({
               budget_period_startdate => "2000-01-01",
               budget_period_enddate => "2999-12-31"
           });
           $schema->resultset("Aqbudget")->create({
               budget_owner_id => 1,
               budget_period_id => $period->id
           }) for (1..1000)
       '
2. Measure the time it takes to load acqui/acqui-home.pl (do it several
   times and keep the average time)
3. Apply the patch
4. Repeat step 2

Signed-off-by: Pedro Amorim <pedro.amorim@ptfs-europe.com>
Signed-off-by: Victor Grousset/tuxayo <victor@tuxayo.net>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>