Kernel: Use ErrorOr in BlockBased and Ext2 filesystem raw read and write

These functions used to return booleans which withheld useful
error information for callers. Internally they would suppress
and convert Error objects. We now log or propagate these errors
up the stack.

Kernel/FileSystem/Ext2FileSystem.h

@@ -122,7 +122,7 @@ private:
     ErrorOr<void> write_ext2_inode(InodeIndex, ext2_inode const&);
     bool find_block_containing_inode(InodeIndex, BlockIndex& block_index, unsigned& offset) const;
 
-    bool flush_super_block();
+    ErrorOr<void> flush_super_block();
 
     virtual StringView class_name() const override { return "Ext2FS"sv; }
     virtual Ext2FSInode& root_inode() override;