s3: add insecure_skip_verify to enable TLS without verifying the certificate

[yvrhdn]

Is your feature request related to a problem? Please describe.
The s3 config block supports an insecure parameter which disables TLS completely. For environments with self-signed certificates it would be nice to support insecure_skip_verify as well. This would enable TLS but not verify the certificate.

Describe the solution you'd like
Add insecure_skip_verify to not verify certificates.

Describe alternatives you've considered
You can probably work around this by adding the self-signed certificates to your authority store, but this isn't always straight-forward.

Additional context
Example code to achieve this using minio-go: minio/minio-go#1019 (comment)

fyi, Loki has this option: https://github.com/grafana/loki/blob/main/pkg/storage/bucket/http/config.go#L12