config: Add fuzz tests

[pellared]

Add fuzz tests for loading the config from JSON and YAML files.
Update the GitHub workflow to run the fuzz tests for 3 minutes. Example: https://github.com/jidicula/go-fuzz-action/blob/main/action.yml

We can also separately look into using OSS-Fuzz. References:

• https://opentelemetry.io/blog/2024/fuzzing-audit-results/
• https://google.github.io/oss-fuzz/getting-started/new-project-guide/go-lang/

EDIT: #6605 created