feat: split current fuse function to fuse request layer and new storage layer.

[IRONICBo]

Background

At present, the storage interface exposed to the outside world is POSIX (fuse), in order to consider the user space to complete the transmission of storage data, consider providing a set of sdk for the business layer to efficiently read the data stored in the back-end without going through the kernel, you can refer to the form of the deployment of the following two main forms of discussion. 1. a single datenlord service, multiple sdk processes to access the data through shared mem + (socket/pipe) to complete the data sharing:

1. a single datenlord service, multiple sdk processes to access the data, through shared mem + (socket/pipe) to complete the data sharing, this time you need to provide a server to the service side. 2. datenlord as a lib, provide the necessary read and write interfaces to the sdk layer, other languages implement the corresponding c-bind to complete the interface access (prefer) The above two ways need us to extract the storage layer of read and write data interface, and provide HDFS-like read and write SDK, in order to ensure that the two access methods are not affected.

Core Modification

1. Migrate memfs to src/fs and rename to datenlordfs.
2. Split memfs to FuseFilesSystem and VirtualFs.
3. Move fuse params to fs_utils.
4. Remove metadata fuse operation.

TODO

1. buffer trait, current implmentation is use BytesMut instead，we need to use common trait.
2. modify direntry to buffer