Optimistic caching TTL value

### Prerequisites

- [X] I have checked the [Wiki](https://github.com/AdguardTeam/AdGuardHome/wiki) and [Discussions](https://github.com/AdguardTeam/AdGuardHome/discussions) and found no answer

- [X] I have searched other issues and found no duplicates

- [X] I want to request a feature or enhancement and not ask a question

### Description

#### What problem are you trying to solve?

The default TTL value in Optimistic caching is 10. TTL of 10 in DNS world is an eternity. 😃

1) If the ip is still valid, no problem.
2) If the ip is not valid, connection issues. Client software will probably timeout in these 10 seconds.

#### Proposed solution

Ability to manually change/ reduce this value (in AdGuardHome.yaml). Users will change this value based on their network setup.

Or is this option already available? I want to reduce this value to 1-3 seconds. Even with a TTL value of 2 seconds, AdGuard Home will have enough time to refresh the DNS entry. Most DNS responses are <200 ms.