Add filename validation for VA image import to prevent invalid characters in disk name.
Previously, filenames extracted from URL could contain special shell characters such as [], (), {}, *, ?, $, etc. These characters may be interpreted by the shell when executing system() commands (e.g., mv), leading to unexpected behavior or command failure.
This patch extracts the disk filename from the URL and validates it using is_invalid_image_name() to reject unsupported characters before proceeding.
Only filenames containing ("a-z","A-Z" ,"0-9" ,"." ,"_" ,"-" ) are allowed.

AN(config)#va image "apv_10_7_0_21" "file://Rel_APV_10_7_0_21[1].qcow2" "qcow2" "file://metadata.ini"
VA data downloading...
Invalid image file name "Rel_APV_10_7_0_21[1].qcow2" in the URL! Allowed characters: "a-z", "A-Z", "0-9", ".", "_", "-"