To help creating/running/… containers using the client for test integration.
This should make test more readable and reduce duplication a bit.
Usage example
```
// Create a default container named foo
id1 := container.Create(t, ctx, client, container.WithName("foo"))
// Run a default container with a custom command
id2 := container.Run(t, ctx, client, container.WithCmd("echo", "hello world"))
```
Signed-off-by: Vincent Demeester <vincent@sbr.pm>
split all non-cli portions into a new internal/test/environment package
Set a test environment on packages instead of creating new ones.
Signed-off-by: Daniel Nephin <dnephin@docker.com>
