feat: support with_copy_to

[guenhter]

This PR supports copying files into the container like this:

DockerContainer("alpine")
    .with_command(["cat", "/tmp/copied.txt"])
    .with_copy_to("/tmp/copied.txt", src)

To support this, I had to change how the container is started: run is not longer used, but instead create and start are used now, in order to be able to make the copy before the container is actually running.

Inspired by testcontainers/testcontainers-rs#730 where I did exactly the same feature for the rust implementation of testcontainers :)

---

No tests are failing

> uv run pytest -v core/tests
...
================================== 306 passed, 1 skipped, 1 warning in 161.30s (0:02:41) ==================================

[guenhter]

Solves #665