Merge in DNS/dnsproxy from fix-unit-tests to master

Squashed commit of the following:

commit 1f287f124348739d946b270988750f7250a9a1ee
Author: Andrey Meshkov <am@adguard.com>
Date:   Thu Oct 20 14:56:08 2022 +0300

    run linter in a separate stage

commit 520743c54abd525b2175e589d055f02cff4bb173
Author: Andrey Meshkov <am@adguard.com>
Date:   Thu Oct 20 14:49:02 2022 +0300

    fix review comments

commit 9ebafc2821ecfe114d1ddadc85019f95d89e6cc1
Author: Andrey Meshkov <am@adguard.com>
Date:   Thu Oct 20 14:29:26 2022 +0300

    fix review comments and fix flaky TestHttpsProxyTrustedProxies

commit 0ae8960b8e2181da5cc41dca28290c268dbf64ee
Author: Andrey Meshkov <am@adguard.com>
Date:   Thu Oct 20 14:05:49 2022 +0300

    stabilize bootstrap timeout test on GH actions

commit e30c4c7989495e92edeebf098fc729dd151582da
Author: Andrey Meshkov <am@adguard.com>
Date:   Thu Oct 20 13:57:27 2022 +0300

    added a comment about rootCAs

commit 60a8c02e8b93c7034f48b3e348837a0d225d4ab8
Merge: 99a3986 515fec8d
Author: Andrey Meshkov <am@adguard.com>
Date:   Thu Oct 20 13:56:05 2022 +0300

    upstream: refactor unit-tests

commit 99a3986969b81aa9b10320937ea719f5a274eec1
Author: Andrey Meshkov <am@adguard.com>
Date:   Thu Oct 20 12:32:52 2022 +0300

    upstream: refactor upstream plain/dot unit-tests

commit 84a7f30ef69020099be6247a466491c3e36cd7ec
Author: Andrey Meshkov <am@adguard.com>
Date:   Thu Oct 20 11:00:32 2022 +0300

    upstream: yet another attempt to fix races