executor: move into tokio crate (#1702)

A step towards collapsing Tokio sub crates into a single `tokio`
crate (#1318).

The executor implementation is now provided by the main `tokio` crate.
Functionality can be opted out of by using the various net related
feature flags.

ci/azure-tsan.yml

@@ -5,8 +5,6 @@ jobs:
     matrix:
       Timer:
         cmd: cargo test -p tokio-timer --test hammer
-      Threadpool:
-        cmd: cargo test -p tokio-executor --tests --features threadpool
   pool:
     vmImage: ubuntu-16.04
   steps:

ci/patch.toml

@@ -2,7 +2,6 @@
 # repository.
 [patch.crates-io]
 tokio = { path = "tokio" }
-tokio-executor = { path = "tokio-executor" }
 tokio-macros = { path = "tokio-macros" }
 tokio-sync = { path = "tokio-sync" }
 tokio-tls = { path = "tokio-tls" }