feat: enhance filesystem support with new syscalls and applications

Created by: hjg0603

• Updated the number of applications in the linker script from 10 to 12.
• Added new applications: 06test_fs and 05test_new_syscalls.
• Implemented sys_openat to support O_CREAT, O_TRUNC, and O_APPEND flags.
• Added sys_ftruncate, sys_fstatat, sys_readv, and sys_writev for enhanced file operations.
• Improved file descriptor management with FD_CLOEXEC support.
• Introduced sys_chdir and sys_getcwd for directory management.
• Added sys_renameat2 for renaming files and directories.
• Enhanced the initproc to include the new test applications.
• Updated the network polling mechanism to optimize performance.
• Added a comprehensive status report on the implementation of various features and functionalities.