Housekeeping (#8)

* Rename the provider to dockerbuild.
* Add Makefile targets required by CI.
* Add per-language test targets compatible with CI.
* Fix broken example yaml.
* Add gitignore exclusions to fix SDK generation in CI.
* Fix lint errors.
* Vendor pulumi CLI via `tools.go` instead of `.pulumi`.
* Consolidate `go.mod`s into one file, with a minimal `go.mod` for the
Go SDK.
* Add codecov.

examples/dotnet/Program.cs

@@ -1,21 +1,18 @@
 using System.Collections.Generic;
 using System.Linq;
 using Pulumi;
-using DockerNative = Pulumi.DockerNative;
+using Dockerbuild = Pulumi.Dockerbuild;
 
 return await Deployment.RunAsync(() => 
 {
-    var myRandomResource = new DockerNative.Random("myRandomResource", new()
+    var myRandomResource = new Dockerbuild.Random("myRandomResource", new()
     {
         Length = 24,
     });
 
     return new Dictionary<string, object?>
     {
-        ["output"] = 
-        {
-            { "value", myRandomResource.Result },
-        },
+        ["value"] = myRandomResource.Result,
     };
 });