submission_package: Move ExeFS and RomFS initialization to its own function

Like the other two bits of factored out code, this can also be put
within its own function. We can also modify the code so that it accepts
a const reference to a std::vector of files, this way, we can
deduplicate the file retrieval.

Now the constructor for NSP isn't a combination of multiple behaviors in
one spot. It's nice and separate.

src/core/file_sys/submission_package.cpp

@@ -53,22 +53,15 @@ NSP::NSP(VirtualFile file_)
         return;
     }
 
+    const auto files = pfs->GetFiles();
+
     if (IsDirectoryExeFS(pfs)) {
         extracted = true;
-        exefs = pfs;
-
-        const auto& files = pfs->GetFiles();
-        const auto romfs_iter =
-            std::find_if(files.begin(), files.end(), [](const FileSys::VirtualFile& file) {
-                return file->GetName().find(".romfs") != std::string::npos;
-            });
-        if (romfs_iter != files.end())
-            romfs = *romfs_iter;
+        InitializeExeFSAndRomFS(files);
         return;
     }
 
     extracted = false;
-    const auto files = pfs->GetFiles();
 
     SetTicketKeys(files);
     ReadNCAs(files);
@@ -212,6 +205,20 @@ bool NSP::ReplaceFileWithSubdirectory(VirtualFile file, VirtualDir dir) {
     return false;
 }
 
+void NSP::InitializeExeFSAndRomFS(const std::vector<VirtualFile>& files) {
+    exefs = pfs;
+
+    const auto romfs_iter = std::find_if(files.begin(), files.end(), [](const VirtualFile& file) {
+        return file->GetName().find(".romfs") != std::string::npos;
+    });
+
+    if (romfs_iter == files.end()) {
+        return;
+    }
+
+    romfs = *romfs_iter;
+}
+
 void NSP::ReadNCAs(const std::vector<VirtualFile>& files) {
     for (const auto& outer_file : files) {
         if (outer_file->GetName().substr(outer_file->GetName().size() - 9) != ".cnmt.nca") {

src/core/file_sys/submission_package.h

@@ -59,6 +59,7 @@ protected:
     bool ReplaceFileWithSubdirectory(VirtualFile file, VirtualDir dir) override;
 
 private:
+    void InitializeExeFSAndRomFS(const std::vector<VirtualFile>& files);
     void ReadNCAs(const std::vector<VirtualFile>& files);
 
     VirtualFile file;