lseek_syscall and close_syscall updates

[namanlalitnyu]

Description

Fixes # (issue)
The following changes include the tests and comments in the code for the lseek_syscall and close_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 lseek_syscall and close_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 lseek_syscall and close_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_lseek_on_file()
• Test B - ut_lind_fs_lseek_on_directory()
• Test C - ut_lind_fs_lseek_invalid_whence()
• Test D - ut_lind_fs_lseek_beyond_file_size()
• Test E - ut_lind_fs_lseek_before_start_of_file()
• Test F - ut_lind_fs_lseek_on_pipe()
• Test G - ut_lind_fs_lseek_on_chardev()
• Test H - ut_lind_fs_lseek_on_epoll()
• Test I - ut_lind_fs_close_chardev()
• Test J - ut_lind_fs_close_pipe()
• Test K - ut_lind_fs_close_socket()
• Test L - ut_lind_fs_close_directory()
• Test M - ut_lind_fs_close_regular_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)

[davidge20]

minor comments, overall great job explaining everything in detail!

[namanlalitnyu]

@davidge20 @Anway-Agte, I have addressed the review comments. Please can you review the changes once?

[davidge20]

lgtm !

[namanlalitnyu]

@yashaswi2000, requesting your review of these changes.
Thanks!

[yashaswi2000]

Great Job, nice comments!

[namanlalitnyu]

@rennergade, requesting your review of these changes.
Thanks!

[rennergade]

This looks quite good though the comment I pointed out is pretty major. I'd double check everything to be consistent with that.