Customizable bootstrap servers in mobileconfig API

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### Prerequisites

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- [x] I am running the latest version
- [x] I checked the documentation and found no answer
- [x] I checked to make sure that this issue has not already been filed

### Issue Details

* **Version of AdGuard Home server:**
* v0.107.0-a.166+176a344a
* **How did you install AdGuard Home:**
* Docker
* **How did you setup DNS configuration:**
* Router
* **If it's a router or IoT, please write device model:**
* VPS
* **CPU architecture:**
* AMD64
* **Operating system and version:**
* Ubuntu 20.04.3 LTS

### Expected Behavior

The latest *. mobileconfig is not working on iOS & macOS. After I installed this profile, I cannot reach any website. `ServerAddresses` may not mean as Bootstrap DNS servers. It works on Code A but not works on Code B.
```
# Code A
DNSProtocol
HTTPS
ServerAddresses

8.8.4.4
8.8.8.8

ServerURL
https://dns.google/dns-query
```
```
# Code B
DNSProtocol
HTTPS
ServerAddresses

8.8.4.4
8.8.8.8

ServerURL
https://my.dns.server/dns-query
```
### Actual Behavior

### Screenshots

Screenshot:

### Additional Information