meson: allow wayland-protocols to be used as wrap
We need to get the "internal" variable if we've built wayland-protocols as a subproject. Wayland-protocols already has al of the infrastructure in place for this, we just need to make use of it. This requires a bump to Meson 0.54, which we had discussed in the past but had no reason to move to. I have installed the .wrap file and checked it in. Due to upstream API changes in the wrapdb meson >= 0.59.0 is required to run `meson wrap install wayland-protocols`, which defeats much the value of being used as a wrap.