Refactor many common flags into openssl.pod

Refactor many common flags into openssl.pod

Options moved: -rand, -writerand, -CApath, -CAfile, -no-CApath, -no-CAfile
Added rand to dgst and srp manpages (they were missing them).
New sections in openssl.pod: Random State Options, Trusted Certificate
Options.
Cleanup and add comments to find-doc-nits
Remove ".in" file support; unless giving specific arguments, this
only runs after configuration

Reviewed-by: Tomas Mraz <tmraz@fedoraproject.org>
Reviewed-by: Dmitry Belyavskiy <beldmit@gmail.com>
Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/10118)