Fix: security vulnerabilities in the codebase

[bhaskar-ram-allam]

This pull request addresses several security vulnerabilities in the Fabric CLI codebase:

1. Updated Go Version:

   • Updated from Go 1.12 to Go 1.21 to address security vulnerabilities in older versions.

2. Plugin System Security:

   • Added path validation to prevent path traversal attacks
   • Implemented command whitelisting to prevent execution of unauthorized commands
   • Added argument sanitization to prevent command injection
   • Enhanced plugin loading with proper validation

3. File Operation Security:

   • Added path validation to prevent path traversal attacks
   • Implemented atomic file writes for configuration files
   • Ensured proper file permissions (0600) for sensitive files
   • Added directory creation with secure permissions (0700)

4. YAML Parsing Security:

   • Created a secure YAML parsing utility to prevent deserialization attacks
   • Added validation of parsed data to ensure integrity
   • Implemented a dedicated plugin loading function with security checks

5. Input Validation:

   • Added comprehensive validation of user input
   • Implemented validation of configuration data
   • Added checks for plugin names and paths

6. Documentation:

   • Updated SECURITY.md with security guidelines and best practices

These changes significantly improve the security posture of the Fabric CLI by addressing all the identified vulnerabilities.