tpl: Fix metrics hint tracking

When tracking for cache hints, track the same template name as the call
to MeasureSince() in Execute.  When referencing a partial "foo", the
value of `n` does not match `templ.Name()` (`partials/foo` versus
`partials/foo.html`), which was caused hints to not be tracked since
there was no existing metric to append the hint to.

Fixes gohugoio#8125

tpl/partials/partials.go

@@ -155,7 +155,7 @@ func (ns *Namespace) Include(name string, contextList ...interface{}) (interface
 	}
 
 	if ns.deps.Metrics != nil {
-		ns.deps.Metrics.TrackValue(n, result)
+		ns.deps.Metrics.TrackValue(templ.Name(), result)
 	}
 
 	return result, nil