I wish fetch-config would not delete the .json config file

It's counterproductive that running `fetch-config` deletes the input `.json` config file.
When I'm debugging issues I want to just edit the file and rerun the `fetch-config` command. The fact that `fetch-config` deletes the file makes this more of a hassle.

And to me it seems like the configuration is overcomplicated (converting to a different `.toml` format, there's also a `.yaml` file there for some reason). It would be way more straightforward if we just specify `.json` file or SSM parameter or whatever as the configuration source, and the CloudWatch agent just leaves that as the source of truth, i.e. always reads from that file or SSM parameter on startup instead of fetching it and storing it in some other format.

Start at the fetch-config command and trace how its JSON input is fetched, converted, and removed; inspect the related configuration-loading and startup paths. Define the desired source-of-truth behavior for JSON files and SSM parameters, then verify that rerunning fetch-config preserves the input and does not require an intermediate format.

Written by the indexing model from the issue text.