content_archive: Add update title detection

This is needed because the title IDs of update NCAs will not use the update title ID. The only sure way to tell is to look for a partition with BKTR crypto.

src/core/file_sys/content_archive.cpp

@@ -258,6 +258,10 @@ NCA::NCA(VirtualFile file_) : file(std::move(file_)) {
         file->ReadBytes(sections.data(), length_sections, SECTION_HEADER_OFFSET);
     }
 
+    is_update = std::find_if(sections.begin(), sections.end(), [](const NCASectionHeader& header) {
+                    return header.raw.header.crypto_type == NCASectionCryptoType::BKTR;
+                }) != sections.end();
+
     for (std::ptrdiff_t i = 0; i < number_sections; ++i) {
         auto section = sections[i];
 
@@ -358,6 +362,10 @@ VirtualFile NCA::GetBaseFile() const {
     return file;
 }
 
+bool NCA::IsUpdate() const {
+    return is_update;
+}
+
 bool NCA::ReplaceFileWithSubdirectory(VirtualFile file, VirtualDir dir) {
     return false;
 }