Ability to partially disable statistics

### Problem Description
While we have the ability to disable the log, all the requests still show up in "statistics". We do not have client history, but we have the requested/resolved names visible for at least 24 hours. This can be a privacy concern for any user who has multiple people sharing the server.

While this was previously requested, I feel that most people who use AdGuard are using it to protect their privacy and these options not being available make AGH a less desirable solution for some.

I have found a workaround by using `chattr +i stats.db` and while the control panel throws `Error: control/stats | Couldn't get statistics data | 500`, it still processes requests normally. The only issue with this workaround is that every time the server needs a restart, you must run `chattr -i` to unlock it, start the server, and then lock it again.

### Proposed Solution
Some more options for what data is saved would be useful. By doing this method, I lose access to the client list. Seeing the clients who submit requests and the quantity of them is more useful to me than domains. For troubleshooting, I might enable statistics again to see if AGH is blocking the site in question, but day to day we usually don't need the stats.

A more privacy focused setup would include

- Option to log only client information (IP) and number of requests
- Option for logging numbers only in statistics, not recording domains
- Option to completely disable statistics
- Lock option in the AdGuardHome.yaml file to prevent the web UI from enabling/disabling it

### Alternatives Considered

A less attractive alternative would include hiding the specifics of the stats from the dashboard with a "hide/show" button, one that may require the password to be re-entered, or possibly using a different password or PIN for added security.

### Additional Information

Whether people are sharing the server in their home with family using a Pi or on a VPS with friends, most people don't want to see other user's requests. Even though the statistics are "anonymous", there are many cases where the requested domain can be tied back to the user who sent the request.