fix: fix unstable tag generation for composite indexes with different column orders

[ucpr]

• Do only one thing
• Non breaking API changes
• Tested

What did this pull request do?

Fix unstable tag generation for composite indexes with different column orders.

User Case Description

When multiple composite indexes exist on the same columns but in different orders, the generated code may have unstable tag output.

Example:

CREATE TABLE users (
    id INT PRIMARY KEY,
    email VARCHAR(255),
    name VARCHAR(255),

    -- composite indexes with different column orders
    INDEX idx_email_name (email, name),
    INDEX idx_name_email (name, email)
);

With a schema like the above, the generated tags can vary between runs:

// First run
Email string `gorm:"index:idx_email_name,priority:1;index:idx_name_email,priority:2"`

// Second run (order may differ)
Email string `gorm:"index:idx_name_email,priority:2;index:idx_email_name,priority:1"`