Updates to "write_syscall" and "pwrite_syscall"

[namanlalitnyu]

Description

Fixes # (issue)
The following changes include the tests and comments in the code for the write_syscall and pwrite_syscall file system calls under RustPosix.
The tests were added to cover all the possible scenarios that might happen when calling the file system_calls write_syscall and pwrite_syscall.

Type of change

• This change just contains the tests for an existing file system call.
• This change contains the minor code changes and comments for write_syscall and pwrite_syscall.
• This change contains code reformatting for existing file system calls.

How Has This Been Tested?

Inorder to run the tests, we need to run cargo test --lib command inside the safeposix-rust directory.

All the tests are present under this directory: lind_project/src/safeposix-rust/src/tests/fs_tests.rs

• Test A - ut_lind_fs_write_read_only_fd()
• Test B - ut_lind_fs_write_to_directory()
• Test C - ut_lind_fs_write_to_epoll()
• Test D - ut_lind_fs_write_to_regular_file()
• Test E - ut_lind_fs_write_to_chardev_file()
• Test F - ut_lind_fs_write_to_sockets()
• Test G - ut_lind_fs_pwrite_read_only_fd()
• Test H- ut_lind_fs_pwrite_to_file()
• Test I- ut_lind_fs_pwrite_to_directory()
• Test J - ut_lind_fs_pwrite_invalid_types()
• Test K - ut_lind_fs_pwrite_to_chardev_file()

Checklist:

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• Any dependent changes have been added to a pull request and/or merged in other modules (native-client, lind-glibc, lind-project)

[namanlalitnyu]

@qianxichen233, Requesting your review of these changes.
Thanks!

[yashaswi2000]

good tests, minor refactoring. good work!

[yashaswi2000]

LGTM

[rennergade]

Great job. Approved!