FindOpenSSL: add target OpenSSL::applink to support OpenSSL's applink feature

Fixes: #20701
6 jobs for !4737 with master in 5 minutes and 5 seconds (queued for 1 second)
detached
Status Name Job ID Coverage
  Build
passed build:debian10-iwyu #4952089
build docker linux

00:01:51

passed build:fedora31-sphinx #4952091
build docker linux linux-3.17

00:05:05

passed build:fedora31-tidy #4952090
build docker linux

00:01:56

 
  External
passed cdash

passed ghostflow-check-master

passed cdash