smbclient.py add SMB share permissions check (issues #186)

[oladush]

This PR implements share permission checks as requested in #186.

Changes:

• READ/WRITE/DELETE access check
• New -check-access flag to verify share permissions
• Supports -no-write-check to skip write/delete tests

Usage examples:

1. Check specific shares:
   `python3 examples/smbclient.py 'test:test@127.0.0.1' -check-access 'MY SHARE, IPC$'`

2. Check all available shares:
   `python3 examples/smbclient.py 'test:test@127.0.0.1' -check-access`

3. Skip write/delete checks (read-only):
   `python3 examples/smbclient.py 'test:test@127.0.0.1' -check-access -no-write-check`

Fixes (#186)

[covertivy]

There exists a better way of enumerating share information: one can request a share information query for level 2 or 502 and the returned struct will also hold a permissions attribute.
This is a much better way to check privileges without manually testing each access possibility by uploading and modifying random files...
It is an important feature for sure but I would advise you implement it differently...

[oladush]

Thanks for the feedback! I’ll check the documentation and rework the permissions check properly.