Add remote TLS certificate verification support, implement Strict and Mutual TLS authentication in BIND and dig (backport to v9.18)

Merged Artem Boldariev requested to merge artem-strict-tls-backport-v9_18 into v9_18

This merge requests contains a backport of the Strict/Mutual TLS support to 9.18 (see !5837 (merged))

Also, it contains small follow-up fixes from:

Closes #3163 (closed)

Edited by Michał Kępień

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