Function parse_version_range 

pub fn parse_version_range(s: &str) -> Option<VersionRange>

Parse a version range string.

Handles expressions like:

• ">=4.14 && <5"
• "^>=2.2"
• ">=2.0 || ==1.9"
• ">=4.14"
• "==1.0"

Returns None if the string is empty or cannot be parsed.