Abstracting coderd into an interface added misdirection because
the interface was never intended to be fulfilled outside of a single
implementation.
This lifts the abstraction, and attaches all handlers to a root struct
named `*coderd.API`.
This enables a "kubernetes_pod" to attach multiple agents that
could be for multiple services. Each agent is required to have
a unique name, so SSH syntax is:
`coder ssh <workspace>.<agent>`
A resource can have zero agents too, they aren't required.
It's possible for websocket close messages to be too long, which cause
them to silently fail without a proper close message. See error below:
```
2022-03-31 17:08:34.862 [INFO] (stdlib) <close_notjs.go:72> "2022/03/31 17:08:34 websocket: failed to marshal close frame: reason string max is 123 but got \"insert provisioner daemon:Cannot encode []database.ProvisionerType into oid 19098 - []database.ProvisionerType must implement Encoder or be converted to a string\" with length 161"
```
* chore: Move httpmw to /coderd directory
httpmw is specific to coderd and should be scoped under coderd
* chore: Move httpapi to /coderd directory
httpapi is specific to coderd and should be scoped under coderd
* chore: Move database to /coderd directory
database is specific to coderd and should be scoped under coderd
* chore: Update codecov & gitattributes for generated files
* chore: Update Makefile
