chore: enclose everything in namespace matar

Signed-off-by: Amneesh Singh <natto@weirdnatto.in>

src/cpu/cpu-impl.cc

@@ -7,6 +7,7 @@
 
 using namespace logger;
 
+namespace matar {
 CpuImpl::CpuImpl(const Bus& bus) noexcept
   : bus(std::make_shared<Bus>(bus))
   , gpr({ 0 })
@@ -142,3 +143,4 @@ CpuImpl::step() {
         }
     }
 }
+}