Use route rather than use thus reducing the number of stack frames (#15301)

Since the move to Chi the number of stack frames has proliferated somewhat catastrophically and we're up to 96 frames with multiple tests of the url outside of a trie which is inefficient.

This PR reduces the number of stack frames by 6 through careful use of Route, moves Captcha into its own router so that it only fires on Captcha routes, similarly for avatars and repo-avatars.

The robots.txt, / and apple-touch-icon.png are moved out of requiring Contexter.

It moves access logger higher in the stack frame because there is no reason why it can't be higher.

Extract from #15186
Contains #15292

routers/api/v1/api.go

@@ -572,10 +572,6 @@ func Routes() *web.Route {
 	}
 	m.Use(context.APIContexter())
 
-	if setting.EnableAccessLog {
-		m.Use(context.AccessLogger())
-	}
-
 	m.Use(context.ToggleAPI(&context.ToggleOptions{
 		SignInRequired: setting.Service.RequireSignInView,
 	}))