CLI: Don't use regex as module attributes

When trying to use OTP28.0-rc1, Elixir fails to compile these modules
because a module attribute cannot be a regex. It is not yet clear
whether it's something to be fixed in Elixir for OTP28 compatibility
or something that accidentally worked in the past, but either way,
using a string as an attribute is equally good and works all OTP
versions, including OTP28.0-rc1.

```
== Compilation error in file lib/rabbitmq/cli/core/command_modules.ex ==
** (ArgumentError) cannot inject attribute @commands_ns into function/macro because cannot escape #Reference<0.2201422310.1333657602.13657>. The supported values are: lists, tuples, maps, atoms, numbers, bitstrings, PIDs and remote functions in the format &Mod.fun/arity
    (elixir 1.18.2) lib/kernel.ex:3729: Kernel.do_at/5
    (elixir 1.18.2) expanding macro: Kernel.@/1
    lib/rabbitmq/cli/core/command_modules.ex:133: RabbitMQ.CLI.Core.CommandModules.make_module_map/2
```

Author: mkuratczyk

deps/rabbitmq_cli/lib/rabbitmq/cli/core/command_modules.ex

@@ -11,7 +11,7 @@ defmodule RabbitMQ.CLI.Core.CommandModules do
 
   import RabbitMQ.CLI.Core.CodePath
 
-  @commands_ns ~r/RabbitMQ.CLI.(.*).Commands/
+  @commands_ns ~S"RabbitMQ.CLI.(.*).Commands"
 
   def module_map(opts \\ %{}) do
     Application.get_env(:rabbitmqctl, :commands) || load(opts)
@@ -130,7 +130,7 @@ defmodule RabbitMQ.CLI.Core.CommandModules do
   end
 
   defp make_module_map(modules, scope) when modules != nil do
-    commands_ns = Regex.recompile!(@commands_ns)
+    commands_ns = Regex.compile!(@commands_ns)
 
     modules
     |> Enum.filter(fn mod ->
@@ -212,7 +212,7 @@ defmodule RabbitMQ.CLI.Core.CommandModules do
   defp command_scopes(cmd) do
     case CommandBehaviour.scopes(cmd) do
       nil ->
-        Regex.recompile!(@commands_ns)
+        Regex.compile!(@commands_ns)
         |> Regex.run(to_string(cmd), capture: :all_but_first)
         |> List.first()
         |> to_snake_case

deps/rabbitmq_cli/lib/rabbitmq/cli/core/os_pid.ex

@@ -7,7 +7,7 @@
 defmodule RabbitMQ.CLI.Core.OsPid do
   @external_process_check_interval 1000
 
-  @pid_regex ~r/^\s*(?<pid>\d+)/
+  @pid_regex ~S"^\s*(?<pid>\d+)"
 
   #
   # API
@@ -27,7 +27,7 @@ defmodule RabbitMQ.CLI.Core.OsPid do
   def read_pid_from_file(pidfile_path, should_wait) do
     case {:file.read_file(pidfile_path), should_wait} do
       {{:ok, contents}, _} ->
-        pid_regex = Regex.recompile!(@pid_regex)
+        pid_regex = Regex.compile!(@pid_regex)
 
         case Regex.named_captures(pid_regex, contents)["pid"] do
           # e.g. the file is empty