tree-wide: unify Bash completions outputs (#103421)

Use $out/share/bash-completion/completions to store the Bash completions

pkgs/tools/filesystems/btrfs-progs/default.nix

@@ -26,7 +26,7 @@ stdenv.mkDerivation rec {
   postPatch = "sed -i s/-O1/-O2/ configure";
 
   postInstall = ''
-    install -v -m 444 -D btrfs-completion $out/etc/bash_completion.d/btrfs
+    install -v -m 444 -D btrfs-completion $out/share/bash-completion/completions/btrfs
   '';
 
   configureFlags = stdenv.lib.optional stdenv.hostPlatform.isMusl "--disable-backtrace";

pkgs/tools/filesystems/ceph/default.nix

@@ -208,12 +208,12 @@ in rec {
   ceph-client = runCommand "ceph-client-${version}" {
       meta = getMeta "Tools needed to mount Ceph's RADOS Block Devices";
     } ''
-      mkdir -p $out/{bin,etc,${sitePackages}}
+      mkdir -p $out/{bin,etc,${sitePackages},share/bash-completion/completions}
       cp -r ${ceph}/bin/{ceph,.ceph-wrapped,rados,rbd,rbdmap} $out/bin
       cp -r ${ceph}/bin/ceph-{authtool,conf,dencoder,rbdnamer,syn} $out/bin
       cp -r ${ceph}/bin/rbd-replay* $out/bin
       cp -r ${ceph}/${sitePackages} $out/${sitePackages}
-      cp -r ${ceph}/etc/bash_completion.d $out/etc
+      cp -r ${ceph}/etc/bash_completion.d $out/share/bash-completion/completions
       # wrapPythonPrograms modifies .ceph-wrapped, so lets just update its paths
       substituteInPlace $out/bin/ceph          --replace ${ceph} $out
       substituteInPlace $out/bin/.ceph-wrapped --replace ${ceph} $out

pkgs/tools/filesystems/yandex-disk/default.nix

@@ -32,12 +32,13 @@ stdenv.mkDerivation rec {
     cd unpacked
     ${rpmextract}/bin/rpmextract $src
 
+    mkdir -p $out/share/bash-completion/completions
     cp -r -t $out/bin usr/bin/*
     cp -r -t $out/share usr/share/*
-    cp -r -t $out/etc etc/*
+    cp -r -t $out/share/bash-completion/completions etc/bash_completion.d/*
 
     sed -i 's@have@${which}/bin/which >/dev/null 2>\&1@' \
-      $out/etc/bash_completion.d/yandex-disk-completion.bash
+      $out/share/bash-completion/completions/yandex-disk-completion.bash
 
     ${patchelf}/bin/patchelf \
       --set-interpreter "$(cat $NIX_CC/nix-support/dynamic-linker)" \