[REF][PHP8.2] Avoid dynamic properties in CRM_Extension_Container_Static

[braders]

Overview

[REF][PHP8.2] Avoid dynamic properties in CRM_Extension_Container_Static

Before

exts set and retreived dynamically, which is deprecated in PHP 8.2. See https://lab.civicrm.org/dev/core/-/issues/3833 for context.

After

PHP 8.2 compatiability.

Full disclosure, I don't really understand how this class is used or what it's for. But it's being used in some tests, exts is only being referenced within this class, and I suspect it's unlikely third-parties are using the exts propery directly (it's unlikely any extensions are using CRM_Extension_Container_Static at all.

[civibot]

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