Swap go-bindata for built-in Go embed

[shoenig]

Fun fact: the current owner of go-bindata become so by hijacking the github repo.

Go now provides a built-in way for embedding statics, via embed

We can replace use of the 3rd party go-bindata tool and go-bindata-assetfs library with go:embed.

Vault has already made the switch: hashicorp/vault#11208

Consul intends to do has done so: hashicorp/consul#10996