mesa: Retire older autotools mesa as mesa18 and create current meson mesa (#19528)

etc/spack/defaults/packages.yaml

@@ -23,8 +23,8 @@ packages:
       daal: [intel-daal]
       elf: [elfutils]
       fftw-api: [fftw]
-      gl: [mesa+opengl, opengl]
-      glx: [mesa+glx, opengl]
+      gl: [mesa+opengl, mesa18+opengl, opengl]
+      glx: [mesa+glx, mesa18+glx, opengl]
       glu: [mesa-glu, openglu]
       golang: [gcc]
       iconv: [libiconv]
@@ -38,6 +38,7 @@ packages:
       mpi: [openmpi, mpich]
       mysql-client: [mysql, mariadb-c-client]
       opencl: [pocl]
+      osmesa: [mesa+osmesa, mesa18+osmesa]
       pil: [py-pillow]
       pkgconfig: [pkgconf, pkg-config]
       rpc: [libtirpc]