Allow role mentions in specific areas

[Den4200]

Description

Since we do not allow the bot to mention roles anymore (b1c0177) except for moderators+ (36330b1) after the incident, this has created a new issue where the bot cannot ping roles where it is actually needed in certain places. This needs to be fixed.

Some of these places include:

• Mod alerts (pings @everyone)
• Mod log (pings @everyone)
• The help channel system (pings @Helpers)
• Syncers (pings @PyDis Core Developers)

There may be some other areas I missed, so please look over the codebase carefully and explicitly allow role mentions where needed.

Implementation

We can use discord.AllowedMentions when sending messages where non-whitelisted role mentions are needed, which will override the global setting. This object can be passed using the allowed_mentions kwarg.