Investiagte the usage `signed_to_duration`

As a follow up I actually think we can investiagte the usage of this method and port all of them to `signed_duration_to_duration`. This makes all `XxxConfig` use a typed struct rather than `ttl: Option` and relying on the implicit contract.

_Originally posted by @tisonkun in https://github.com/apache/opendal/pull/7983#discussion_r3717225084_

Search the repository for `signed_to_duration`, `signed_duration_to_duration`, and `XxxConfig` to map every usage and affected configuration type. Read the surrounding conversion and configuration code first; the work is done when usages are migrated and the configs use typed structs instead of `ttl: Option` with an implicit contract.

Written by the indexing model from the issue text.