Common: Add Random utilities

This makes it easier to generate random numbers or fill a buffer with
random data in a cryptographically secure way.

This also replaces existing usages of RNG functions in the codebase:

* <random> is pretty hard to use correctly, and std::random_device does
  not give enough guarantees about its results (it's
  implementation-defined, non cryptographically secure and could be
  deterministic on some platforms).
  Doing things correctly is error prone and verbose.

* rand() is terrible and should not be used especially in crypto code.

Source/Core/Common/Common.vcxproj

@@ -142,6 +142,7 @@
     <ClInclude Include="PcapFile.h" />
     <ClInclude Include="Profiler.h" />
     <ClInclude Include="QoSSession.h" />
+    <ClInclude Include="Random.h" />
     <ClInclude Include="Result.h" />
     <ClInclude Include="ScopeGuard.h" />
     <ClInclude Include="SDCardUtil.h" />
@@ -206,6 +207,7 @@
     <ClCompile Include="PcapFile.cpp" />
     <ClCompile Include="Profiler.cpp" />
     <ClCompile Include="QoSSession.cpp" />
+    <ClCompile Include="Random.cpp" />
     <ClCompile Include="SDCardUtil.cpp" />
     <ClCompile Include="SettingsHandler.cpp" />
     <ClCompile Include="StringUtil.cpp" />
@@ -250,4 +252,4 @@
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.targets" />
   <ImportGroup Label="ExtensionTargets">
   </ImportGroup>
-</Project>
+</Project>