fix: ensure AddIndex, AddConstraint, RemoveIndex and RemoveConstraint are in correct order

[tsifrer]

Description

Ensures migration generator now correctly orders AddIndex , AddConstraint, RemoveIndex, RemoveConstraint when adding/removing a new indexed field or constraint field to a model.

Motivation and Context

When adding a new field on an existing model, and using that field in as an index or a constraint, the migration creates operations in the wrong order.
Going from this model:

class OldWidget(models.Model):
    id = fields.IntField(pk=True)

to this model:

class OldWidget(models.Model):
    id = fields.IntField(pk=True)
    value = fields.IntField()
    
    class Meta:
        indexes = [Index(fields=["value"])]

would generate a migration file with operations in order: [AddIndex, AddField] causing migration to fail as it can't add an index to a non existing field.
This PR fixes this order.

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added the changelog accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[codspeed-hq]

Merging this PR will not alter performance

✅ 24 untouched benchmarks

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_{Comparing tsifrer:fix-index-order (18400aa) with develop (314273c)}