DEV: Correct typos and spelling mistakes (#12812)

Over the years we accrued many spelling mistakes in the code base. 

This PR attempts to fix spelling mistakes and typos in all areas of the code that are extremely safe to change 

- comments
- test descriptions
- other low risk areas

lib/plugin/instance.rb

@@ -591,7 +591,7 @@ class Plugin::Instance
     end
   end
 
-  # note, we need to be able to parse seperately to activation.
+  # note, we need to be able to parse separately to activation.
   # this allows us to present information about a plugin in the UI
   # prior to activations
   def activate!
@@ -816,7 +816,7 @@ class Plugin::Instance
   end
 
   # Register a new UserApiKey scope, and its allowed routes. Scope will be prefixed
-  # with the (parametetized) plugin name followed by a colon.
+  # with the (parameterized) plugin name followed by a colon.
   #
   # For example, if discourse-awesome-plugin registered this:
   #