Mesa 26 update work

Hello,

I wanted to let you know I've done work on updating the Mesa ports to
version 26.0.5 and would like to discuss and work with you about it. :)

https://codeberg.org/kenrap/freebsd-ports/pulls/4

One of the things I want to mention is about the mesa-dri and mesa-libs
split. I found that merging them back to graphics/mesa made it so that I
can launch Plasma Wayland after much build testing and experimentation.
Beforehand, Plasma Wayland would act as if the radeonsi driver didn't exist
(it was installed) until I did this approach.

Also in Mesa 26, libosmesa got removed and there are some ports that still
have it as a build option or hardcodes the dep.

I'm hoping to get Mesa updated in the ports tree to help the community. :)

Regards,
Kenneth