feat: skip-execution flag for migrate command

[stbestichhh]

Pull Request check-list

Please make sure to review and check all of these items:

• Does npm run test pass with this change (including linting)?
• Does the description below contain a link to an existing issue (Closes #[issue]) or a description of the issue you are solving?
• Have you added new tests to prevent regressions?
• Is a documentation update included (if this change modifies existing APIs, or introduces new ones)? docs: skipping migration execution in Sequelize website#825

Description of change

Skipping Migration Execution

In some cases you may want to mark migrations as completed without actually executing their SQL. This can be useful when:
- The database schema was applied manually
- You are syncing migration history between environments
- You are adopting Sequelize CLI for an existing database
- You want to avoid re-running destructive or already-applied changes

For this purpose, I have implemented a custom --skip-execution flag.