feat: Support YAML as format for the config file

### Use Case

Hi,

we are doing a lot of our configuration using YAML (since we're using Kubernetes), and we would like it to be possible to also use YAML as a file format for the Telegraf config file.

I know there is a large amount of dependencies on TOML, so this might be difficult/a lot of work.

Possible way to implement this, might be to use Viper for the configuration loading and Cobra for the commands
https://github.com/spf13/viper
https://github.com/spf13/cobra

### Expected behavior

Possible to use YAML for the config file.

### Actual behavior

Only TOML is supported/

### Additional info

_No response_

Start by tracing Telegraf's configuration-loading entry points and identifying the TOML-specific assumptions across the repository. Assess whether the proposed Viper and Cobra dependencies fit the existing configuration and command paths. Done means a YAML config file is accepted while existing TOML configuration continues to work.

Written by the indexing model from the issue text.