Avoid escaping paths when editing credentials

`Shellwords.escape` escapes unquoted spaces with a backslash, but
Windows does not treat backslash as an escape character.  Escaping is
also a problem when paths are expressed in shortened 8.3 format (e.g.
`C:\Users\RubyOn~1\AppData\Local\Temp\...`) because a backslash will be
erroneously added before the `~`.

We can avoid the need to escape by using `system(command_name, *args)`
instead of `system(command_line)`, but we must still support
`ENV["EDITOR"]` values that embed command line arguments, such as
`subl -w`.

This commit changes to `system(command_name, *args)`, but uses
`Shellwords.split` to extract any embedded arguments from
`ENV["EDITOR"]`.  This requires that Windows users put quotes around the
entire path of their editor if it contains spaces, such as:

```
SET EDITOR="C:\Program Files\Microsoft VS Code\Code.exe" -w
```

In other words, the following are **not** supported on Windows:

```
SET "EDITOR=C:\Program Files\Microsoft VS Code\Code.exe"
SET EDITOR=C:\Program Files\Microsoft VS Code\Code.exe
SET EDITOR=C:\"Program Files"\"Microsoft VS Code"\Code.exe -w
SET EDITOR=C:\Program^ Files\Microsoft^ VS^ Code\Code.exe -w
SET EDITOR=C:\Program` Files\Microsoft` VS` Code\Code.exe -w
```

Fixes #41617 (again).
Closes #44890.

railties/lib/rails/commands/credentials/credentials_command.rb

@@ -92,7 +92,7 @@ def ensure_credentials_have_been_added
 
         def change_credentials_in_system_editor
           credentials.change do |tmp_path|
-            system("#{ENV["EDITOR"]} #{Shellwords.escape(tmp_path)}")
+            system(*Shellwords.split(ENV["EDITOR"]), tmp_path.to_s)
           end
         end
 

railties/test/commands/credentials_test.rb

@@ -37,7 +37,7 @@ class Rails::Command::CredentialsCommandTest < ActiveSupport::TestCase
   end
 
   test "edit command does not overwrite by default if credentials already exists" do
-    run_edit_command(editor: "eval echo api_key: abc >")
+    run_edit_command(editor: 'ruby -e "File.write ARGV[0], %(api_key: abc)"')
     assert_match(/api_key: abc/, run_show_command)
 
     run_edit_command