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

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

pkgs/tools/virtualization/awsebcli/default.nix

@@ -83,8 +83,8 @@ in with localPython.pkgs; buildPythonApplication rec {
   ];
 
   postInstall = ''
-    mkdir -p $out/etc/bash_completion.d
-    mv $out/bin/eb_completion.bash $out/etc/bash_completion.d
+    mkdir -p $out/share/bash-completion/completions
+    mv $out/bin/eb_completion.bash $out/share/bash-completion/completions/
   '';
 
   meta = with stdenv.lib; {