LibCoreDump+CrashDaemon: Add and use CoreDump::Backtrace

Creating a backtrace from a crashdump already existed as a few
standalone functions in CrashDaemon. This patch refactors the code
required for this to make it generally usable and moves it to
CoreDump::Backtrace, which provides both raw data as well as
stringification.

Libraries/LibCoreDump/CMakeLists.txt

@@ -1,6 +1,7 @@
 set(SOURCES
+    Backtrace.cpp
     Reader.cpp
 )
 
 serenity_lib(LibCoreDump coredump)
-target_link_libraries(LibCoreDump LibC LibCore)
+target_link_libraries(LibCoreDump LibC LibCore LibDebug)