Improve definition of a few placeholder packages (#48730)

* Improve definition of a few placeholder packages
   These packages are placeholders for vendor provided software,
   that is not buildable, and should be declared as external.
* ibm-java: remove package, as asked by maintainer

etc/spack/defaults/packages.yaml

@@ -36,7 +36,7 @@ packages:
       go-or-gccgo-bootstrap: [go-bootstrap, gcc]
       iconv: [libiconv]
       ipp: [intel-oneapi-ipp]
-      java: [openjdk, jdk, ibm-java]
+      java: [openjdk, jdk]
       jpeg: [libjpeg-turbo, libjpeg]
       lapack: [openblas, amdlibflame]
       libc: [glibc, musl]
@@ -73,15 +73,27 @@ packages:
     permissions:
       read: world
       write: user
+  cray-fftw:
+    buildable: false
+  cray-libsci:
+    buildable: false
   cray-mpich:
     buildable: false
   cray-mvapich2:
     buildable: false
+  cray-pmi:
+    buildable: false
   egl:
     buildable: false
+  essl:
+    buildable: false
   fujitsu-mpi:
     buildable: false
+  fujitsu-ssl2:
+    buildable: false
   hpcx-mpi:
     buildable: false
+  mpt:
+    buildable: false
   spectrum-mpi:
     buildable: false