FS.Archive: Clean up treatment of archives and their handles

- Refactor FS::Archive internals to make Archive creation and lifetime
  management clearer.
- Remove the "Archive as a File" hack.
- Implement 64-bit Archive handles.

src/core/file_sys/archive_romfs.h

@@ -20,7 +20,6 @@ namespace FileSys {
 class Archive_RomFS final : public ArchiveBackend {
 public:
     Archive_RomFS(const Loader::AppLoader& app_loader);
-    ~Archive_RomFS() override;
 
     std::string GetName() const override { return "RomFS"; }
 
@@ -76,37 +75,9 @@ public:
      */
     std::unique_ptr<DirectoryBackend> OpenDirectory(const Path& path) const override;
 
-    /**
-     * Read data from the archive
-     * @param offset Offset in bytes to start reading data from
-     * @param length Length in bytes of data to read from archive
-     * @param buffer Buffer to read data into
-     * @return Number of bytes read
-     */
-    size_t Read(const u64 offset, const u32 length, u8* buffer) const override;
-
-    /**
-     * Write data to the archive
-     * @param offset Offset in bytes to start writing data to
-     * @param length Length in bytes of data to write to archive
-     * @param buffer Buffer to write data from
-     * @param flush  The flush parameters (0 == do not flush)
-     * @return Number of bytes written
-     */
-    size_t Write(const u64 offset, const u32 length, const u32 flush, u8* buffer) override;
-
-    /**
-     * Get the size of the archive in bytes
-     * @return Size of the archive in bytes
-     */
-    size_t GetSize() const override;
-
-    /**
-     * Set the size of the archive in bytes
-     */
-    void SetSize(const u64 size) override;
-
 private:
+    friend class File_RomFS;
+
     std::vector<u8> raw_data;
 };