Userland: Convert TLS::TLSv12 to a Core::Stream::Socket

This commit converts TLS::TLSv12 to a Core::Stream object, and in the
process allows TLS to now wrap other Core::Stream::Socket objects.
As a large part of LibHTTP and LibGemini depend on LibTLS's interface,
this also converts those to support Core::Stream, which leads to a
simplification of LibHTTP (as there's no need to care about the
underlying socket type anymore).
Note that RequestServer now controls the TLS socket options, which is a
better place anyway, as RS is the first receiver of the user-requested
options (though this is currently not particularly useful).

Userland/Libraries/LibGemini/CMakeLists.txt

@@ -1,6 +1,5 @@
 set(SOURCES
     Document.cpp
-    GeminiJob.cpp
     GeminiRequest.cpp
     GeminiResponse.cpp
     Job.cpp