[REF][PHP8.2] Declare campaigns property

[braders]

Overview

Declare campaigns property in CRM_Report_Form.

Before

17 different report classes call addCampaignFields, which was dyamically setting $this->campaigns and therefore triggering a deprcation notice on PHP 8.2.

After

The campaigns property is properly declared. This should reduce the number of tests failing on PHP 8.2.

Comments

There is still lots more to do on reports - this is just 1 step towards full PHP 8.2 compatiability.

[civibot]

(Standard links)

• If you are reviewing this pull-request, you may wish to consult the test sites and the Review Standards (long template, short template).

[colemanw]

Nice @braders