[Bug]: retain_unknown_options incorrectly assumes unknown arguments are consecutive

### What happened?

See #22422

retain_unknown_options first parses all known arguments, then parses the unknown arguments assuming they are consecutive. To illustrate this issue, let's look at this execution:

```
run_pipeline.py --unknown_arg --known_arg=foo bar
```

We first parse the known arguments, and are left with `unknown_args = ['--unknown_arg', 'bar']`. Our logic then assumes `bar` is the value for an unknown option called `unknown_arg`.

### Issue Priority

Priority: 2

### Issue Component

Component: sdk-py-core

Locate retain_unknown_options in the Python SDK core and reproduce the example with unknown_arg and known_arg. Add coverage for nonconsecutive unknown arguments, and consider the issue done when `bar` is not incorrectly treated as the value of `unknown_arg`.

Written by the indexing model from the issue text.