feat: support with_copy_to (#976)

This PR supports copying files into the container before startup time:

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

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 https://github.com/testcontainers/testcontainers-rs/pull/730
where I did exactly the same feature for the rust implementation of
testcontainers :)

----

No tests are failing

```bash
> uv run pytest -v core/tests
...
======================================= 316 passed, 1 skipped in 160.87s (0:02:40) ========================================
```

Co-authored-by: David Ankin <daveankin@gmail.com>