refactor(services)!: use typed durations for moka configs

[subotac]

Which issue does this PR close?

Closes #8025

Rationale for this change

Moka and MiniMoka are the remaining services that keep cache durations as strings and parse them again during backend construction. Their builders also format Duration::as_secs(), which truncates subsecond values
before parsing.

What changes are included in this PR?

• Store Moka and MiniMoka TTL/TTI config values as SignedDuration.
• Convert configured values with signed_duration_to_duration
• Keep builder-provided Duration values as lossless overrides
• Add config parsing and builder precision regression tests

Are there any user-facing changges?

Yes. MokaConfig and MiniMokaConfig now expose Option<SignedDuration> for time_to_live and time_to_idle instead of Option<String>. String-based configuration continues to accept duration values such as
1500ms

[Xuanwo]

Hold on this PR until our next patch version released.