Add check if index exists in migrations

[GuangHa]

Is there an existing issue for this?

• I have searched the existing issues

Current Behavior

There is a migration that drops an index in the version 8.3.19

https://github.com/neos/neos-development-collection/pull/4236/files

ALTER TABLE neos_contentrepository_domain_model_nodedata DROP INDEX IDX_CE6515692D45FE4D, ADD UNIQUE INDEX UNIQ_CE6515692D45FE4D (movedto)

If we run a ./flow doctrine:migrate when the index does not exist then it will run into an error.

Expected Behavior

Add a check if the index exists and only drop when the index exist to prevent the exception while running ./flow doctrine:migrate.

Steps To Reproduce

No response

Environment

- Flow: 8.3.13
- Neos: 8.3.19
- PHP: 8.1 / 8.3

Anything else?

See also https://neos-project.slack.com/archives/C050C8FEK/p1737539317664469