Enable feedback plugin by default on POWER

In order to get a bit more information about the usage of the PowerPC architecture we should try to see if we can enable the feedback plugin by default (with instructions to disable available for the users).

This should be part of future releases.

We ideally want to add a phrasing about why we enable it on that ARCH (the foundation is investing in PPC testing and needs to understand better the usage or MariaDB on that platform).