Pull request: 4745 Fix DHCP hostnames

Merge in DNS/adguard-home from 4745-fix-dhcp-hostnames to master

Closes #4745.

Squashed commit of the following:

commit fe03c8eda6c8ee35a10eb5f5a8e4d4d0c7373246
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Tue Aug 23 18:16:16 2022 +0300

    dhcpd: imp code, naming

commit 7a7129268917d99ba16781b7f2e9bfb7ae84ff3e
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Tue Aug 23 18:10:12 2022 +0300

    dhcpd: add tests

commit bb14a4a62df1eed6492d30f622c3e22da9a6f4be
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Tue Aug 23 14:58:29 2022 +0300

    dhcpd: imp code, docs

commit 2ada39f994cb9dbb2208d47a588eb72056bb5306
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Tue Aug 23 14:44:35 2022 +0300

    all: log changes

commit cbd3ed254865921be09376097dac9f5926b2349a
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Tue Aug 23 14:40:54 2022 +0300

    dhcpd: imp option 81

commit 64dabb52560f5edc08f17aadaa43172a5d74463d
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Tue Aug 23 14:10:15 2022 +0300

    dhcpd: fix empty hostname in static lease

commit 0df5d10d0d94863b9bbab28129bcc3436fb71222
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Tue Aug 23 13:34:31 2022 +0300

    dhcpd: report dupl hostnames of static lease

CHANGELOG.md

@@ -30,9 +30,11 @@ and this project adheres to
 
 ### Fixed
 
+- Dynamic leases created with empty hostnames ([#4745]).
 - Unnecessary logging of non-critical statistics errors ([#4850]).
 
 [#2993]: https://github.com/AdguardTeam/AdGuardHome/issues/2993
+[#4745]: https://github.com/AdguardTeam/AdGuardHome/issues/4745
 [#4850]: https://github.com/AdguardTeam/AdGuardHome/issues/4850