Rename Pleroma.Mix.Tasks.Common -> Mix.Pleroma and import it's functions

instead of aliasing

This seems to be the convention for functions that can be reused between
different mix tasks in all Elixir projects I've seen and it gets rid on
an error message when someone runs mix pleroma.common

Also in this commit by accident:
- Move benchmark task under a proper namespace
- Insert a space after the prompt

lib/mix/tasks/pleroma/uploads.ex

@@ -4,7 +4,7 @@
 
 defmodule Mix.Tasks.Pleroma.Uploads do
   use Mix.Task
-  alias Mix.Tasks.Pleroma.Common
+  import Mix.Pleroma
   alias Pleroma.Upload
   alias Pleroma.Uploaders.Local
   require Logger
@@ -24,7 +24,7 @@ defmodule Mix.Tasks.Pleroma.Uploads do
   """
   def run(["migrate_local", target_uploader | args]) do
     delete? = Enum.member?(args, "--delete")
-    Common.start_pleroma()
+    start_pleroma()
     local_path = Pleroma.Config.get!([Local, :uploads])
     uploader = Module.concat(Pleroma.Uploaders, target_uploader)
 
@@ -38,10 +38,10 @@ defmodule Mix.Tasks.Pleroma.Uploads do
       Pleroma.Config.put([Upload, :uploader], uploader)
     end
 
-    Common.shell_info("Migrating files from local #{local_path} to #{to_string(uploader)}")
+    shell_info("Migrating files from local #{local_path} to #{to_string(uploader)}")
 
     if delete? do
-      Common.shell_info(
+      shell_info(
         "Attention: uploaded files will be deleted, hope you have backups! (--delete ; cancel with ^C)"
       )
 
@@ -78,7 +78,7 @@ defmodule Mix.Tasks.Pleroma.Uploads do
       |> Enum.filter(& &1)
 
     total_count = length(uploads)
-    Common.shell_info("Found #{total_count} uploads")
+    shell_info("Found #{total_count} uploads")
 
     uploads
     |> Task.async_stream(
@@ -90,7 +90,7 @@ defmodule Mix.Tasks.Pleroma.Uploads do
             :ok
 
           error ->
-            Common.shell_error("failed to upload #{inspect(upload.path)}: #{inspect(error)}")
+            shell_error("failed to upload #{inspect(upload.path)}: #{inspect(error)}")
         end
       end,
       timeout: 150_000
@@ -99,10 +99,10 @@ defmodule Mix.Tasks.Pleroma.Uploads do
     # credo:disable-for-next-line Credo.Check.Warning.UnusedEnumOperation
     |> Enum.reduce(0, fn done, count ->
       count = count + length(done)
-      Common.shell_info("Uploaded #{count}/#{total_count} files")
+      shell_info("Uploaded #{count}/#{total_count} files")
       count
     end)
 
-    Common.shell_info("Done!")
+    shell_info("Done!")
   end
 end