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_sdmc.h

@@ -80,36 +80,6 @@ public:
      */
     std::unique_ptr<DirectoryBackend> OpenDirectory(const Path& path) const override;
 
-    /**
-     * Read data from the archive
-     * @param offset Offset in bytes to start reading archive from
-     * @param length Length in bytes to read data 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;
-
     /**
      * Getter for the path used for this Archive
      * @return Mount point of that passthrough archive