withType should be for end users over custom create factories

[matt-gadd]

Enhancement

With https://github.com/dojo/framework/pull/819, there is simply no need to have these separate bespoke create factories such as createIcacheMiddleware anymore. The end user can use withType to stamp the types and that means we don't have to flip flop between separate exports for typed and untyped middleware.

before:

import { createIcacheMiddleware } from '@dojo/framework/core/middleware/icache'

const myIcache = createIcacheMiddleware<{ foo: string }();

after:

import icache from '@dojo/framework/core/middleware/icache'

const myIcache = icache.withType<{ foo: string }();

[agubler]

To note these two aren't quite like for like, for example the createIcacheMiddleware takes an interface for the state but the withType requires the API of the actual middleware, in this case it's something like ICacheResult<StateInterface>:

import icache, { ICacheResult } from '@dojo/framework/core/middleware/icache'

const myIcache = icache.withType<ICacheResult<{ foo: string }>>();