Add warning to [p]set api if <>s are included in secret

[giplgwm]

Description of the changes

Closes #6253
For every given secret, check if its wrapped in <>, if it is, add a message to an embed with a warning that that secret may not be set properly. I tested this on a local instance of the bot and it seems to be working as expected. The warning is also logged

Have the changes in this PR been tested?

Yes

[giplgwm]

@Drapersniper I added the changes requested in your comments as another commit on the PR, thanks

[Kreusada]

Just a couple of suggested changes to improve readability.

[Kreusada]

Wrapping the command examples with inline marks may be appropriate to improve readability.

Suggested change

	"You may have failed to properly format your {api_service_name}. If you were told to enter a key"
	" with an example such as [p]set api {service} api_key <your_api_key_here>, and your API key"
	" was HREDFGWE, make sure to run [p]set api {service} api_key HREDFGWE, and not "
	" [p]set api {service} api_key <HREDFGWE>"
	"You may have failed to properly format your {api_service_name}. If you were told to enter a key"
	" with an example such as `[p]set api {service} api_key <your_api_key_here>`, and your API key"
	" was `HREDFGWE`, make sure to run `[p]set api {service} api_key HREDFGWE` and not "
	" `[p]set api {service} api_key <HREDFGWE>`."

[Kreusada]

It isn't necessary to give this warning inside of an embed, when there is already text content (it would make things more complicated, such as having to check if an embed is requested in the current channel). Instead, you could add line breaks under the original message and put the warning text there. Something like this would suffice:

angle_bracket_warning = None # define this before iterating through tokens
for api_service_name, token in tokens.items():
    ...

message = _("`{service}` API tokens have been set.").format(service=service)
if angle_bracket_warning:
    message += "\n\n" + _("**Warning:** ") + _(angle_bracket_warning)
await ctx.send(message)

Remember to remove the embed definition on line 3636.