Add --no-session-cache flag

### Describe the feature or problem you'd like to solve

Add a flag that blocks caching the session (to avoid cluttering up session list in `copilot --resume`)

### Proposed solution

Put session caching behind a flag (default TRUE) which can be overridden by the argument `--no-session-cache` so that the user can manually block caching for a session that is expected to be disposable. This would be especially helpful for use together with `copilot --no-session-cache --prompt ...` since prompt calls are virtually never going to require `--resume`ing.

### Example prompts or workflows

```console
$ copilot --no-session-cache --prompt "..."
# The prompt session is not cached
$ copilot --resume
# The list of cached sessions does NOT contain the `--prompt` call above.

### Additional context

_No response_

Start at the CLI argument parsing entry point and trace how sessions are added to the cache used by `copilot --resume`. Exercise `copilot --no-session-cache --prompt "..."`, then run `copilot --resume`; done means the prompt session is absent from the cached session list while normal sessions remain cached.

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