[Feature] Update OpenSSL bundled with Icinga 2 independent of Icinga 2 itself

[Al2Klimov]

If OpenSSL X.Y shipped with Icinga 2 gets a patch level security update vX.Y.Z, but there's no Icinga 2 bugfix release yet, users can already do this:

https://community.icinga.com/t/how-to-update-openssl-bundled-with-icinga-2-on-windows/11454/2

Manually.

On every single Windows agent.

Or! The IfW repo also hoards OpenSSL DLLs for an addition to its update mechanism.

[Al2Klimov]

This is our source for OpenSSL DLLs: https://slproweb.com/products/Win32OpenSSL.html

It mirrors only the latest ones and must be checked periodically.