hle/service: Replace global system instance calls with instance-based ones

Migrates the HLE service code off the use of directly accessing the
global system instance where trivially able to do so.

This removes all usages of Core::CurrentProcess from the service code,
only 8 occurrences of this function exist elsewhere. There's still quite
a bit of "System::GetInstance()" being used, however this was able to
replace a few instances.

src/core/hle/service/bcat/bcat.cpp

@@ -6,8 +6,9 @@
 
 namespace Service::BCAT {
 
-BCAT::BCAT(std::shared_ptr<Module> module, FileSystem::FileSystemController& fsc, const char* name)
-    : Module::Interface(std::move(module), fsc, name) {
+BCAT::BCAT(Core::System& system, std::shared_ptr<Module> module,
+           FileSystem::FileSystemController& fsc, const char* name)
+    : Interface(system, std::move(module), fsc, name) {
     // clang-format off
     static const FunctionInfo functions[] = {
         {0, &BCAT::CreateBcatService, "CreateBcatService"},