More privatization, and some error helpers (#2976)

* More privatization, and some error helpers

This makes a lot more things private. Continued from #2967, fixes #2984
Adds public methods for various things.

Below is a brief summary of things available elsewhere, though this
particular set of changes may warrant a detailed section in the release notes.

 - bot.db.locale -> redbot.core.i18n.get_locale
   - Note: This one already existed.
 - bot.db.help -> redbot.core.commands.help.HelpSettings
 - bot db whitelist/blaclist? -> bot.allowed_by_whitelist_blacklist
   - This has also been made a single cannonical function for this
   purpose including check usage
 - bot color? -> bot.get_embed_color/bot.get_embed_colour
 - bot.id.api_tokens? ->

   - bot.get_shared_api_tokens
   - bot.set_shared_api_tokens
   - bot.remove_shared_api_tokens

 -bot.db.prefix -> bot.get_valid_prefixes
   - (Note: This is a wrapper around bot.get_prefix)

 Other changes include
  - removing `bot.counter` as it was never used anywhere
  - Adding properties with helpful error messages for moved and renamed
  things
  - making bot.uptime a property with an error on set
  - adding a migration to the bot config for shared_api_tokens

* Remove overly encompassing message redaction, eval is a risk, dont run in dev if you cant manage it

* address Flame's feedback

* rephrase example

* changelog extras

* You saw nothing

redbot/core/core_commands.py

@@ -87,7 +87,7 @@ class CoreLogic:
 
         for name in cog_names:
             try:
-                spec = await bot.cog_mgr.find_cog(name)
+                spec = await bot._cog_mgr.find_cog(name)
                 if spec:
                     cogspecs.append((spec, name))
                 else:
@@ -1146,7 +1146,7 @@ class Core(commands.Cog, CoreLogic):
         """
         if ctx.channel.permissions_for(ctx.me).manage_messages:
             await ctx.message.delete()
-        await ctx.bot._config.api_tokens.set_raw(service, value=tokens)
+        await ctx.bot.set_shared_api_tokens(service, **tokens)
         await ctx.send(_("`{service}` API tokens have been set.").format(service=service))
 
     @commands.group()
@@ -2198,7 +2198,7 @@ class Core(commands.Cog, CoreLogic):
     async def rpc_load(self, request):
         cog_name = request.params[0]
 
-        spec = await self.bot.cog_mgr.find_cog(cog_name)
+        spec = await self.bot._cog_mgr.find_cog(cog_name)
         if spec is None:
             raise LookupError("No such cog found.")