Deservicify core (#2458)

* De-servicify router (mostly)

Still uses the redraw service, but it no longer has an intermediate
service of its own.

Also, did a *lot* of test deduplication in this. About 30-40% of the
router service tests were already tested on the main router API instance
itself.

Bundle size decreased from 9560 to 9548 bytes min+gzip.

* Merge `m.mount` + `m.redraw`, update router

Simplifies the router and redraw mechanism, and makes it much easier to
keep predictable.

Bundle size down to 9433 bytes min+gzip, docs updated accordingly.

* Make `mithril/render` just return the `m.render` function directly.

* Deservicify `m.render`, revise `m.route`

- You now have to use `mithril/render/render` directly if you want an
  implicit redraw function. (This will likely be going away in v3.)
- Revise `m.route` to only `key` components

* Add `redraw` to `m.render`, deservicify requests

* Test error logging

* Update docs + changelog [skip ci]

docs/route.md

@@ -206,7 +206,7 @@ Argument            | Type                 | Description
 
 #### How it works
 
-Routing is a system that allows creating Single-Page-Applications (SPA), i.e. applications that can go from a "page" to another without causing a full browser refresh.
+Routing is a system that allows creating Single Page Applications (SPA), i.e. applications that can go from a "page" to another without causing a full browser refresh.
 
 It enables seamless navigability while preserving the ability to bookmark each page individually, and the ability to navigate the application via the browser's history mechanism.
 
@@ -336,6 +336,8 @@ Or even use the [`history state`](#history-state) feature to achieve reloadable
 
 `m.route.set(m.route.get(), null, {state: {key: Date.now()}})`
 
+Note that the key parameter works only for component routes. If you're using a route resolver, you'll need to use a [single-child keyed fragment](keys.md), passing `key: m.route.param("key")`, to accomplish the same.
+
 #### Variadic routes
 
 It's also possible to have variadic routes, i.e. a route with an argument that contains URL pathnames that contain slashes:
@@ -739,7 +741,7 @@ m.route(document.body, "/", {
 In certain situations, you may find yourself needing to interoperate with another framework like React. Here's how you do it:
 
 - Define all your routes using `m.route` as normal, but make sure you only use it *once*. Multiple route points are not supported.
-- When you need to remove routing subscriptions, use `m.mount(root, null)`, using the same root you used `m.route(root, ...)` on.
+- When you need to remove routing subscriptions, use `m.mount(root, null)`, using the same root you used `m.route(root, ...)` on. `m.route` uses `m.mount` internally to hook everything up, so it's not magic.
 
 Here's an example with React: