Only actually needed servers should be listed and none is then implied
if no servers are listed.
Outputs a warning if "none" is still set as a server.
Closes#18466
For ASN.1 tags with indefinite length, curl's own parser for TLS
backends that do not support certificate inspection calls itself
recursively. A malicious server certificate can then lead to high
recursion level exhausting the stack space.
This PR limits the recursion level to 16 which should be safe on all
architectures.
Added unit test 1657 to verify behaviour.
Fixes#16135
Reported-by: z2_
Closes#16137