[Issue] Add UpToDateThemes validator to setup:db:status

[m2-assistant]

This issue is automatically created based on existing pull request: #39383: Add UpToDateThemes validator to setup:db:status

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Description (*)

Running bin/magento setup:db:status right now does not check whether there is a theme update. If the only change in the deploy is a theme being added, bin/magento setup:db:status will now show;

$ bin/magento setup:db:status
All modules are up to date.

However if you were to run bin/magento setup:upgrade, you'd get this message;

$ bin/magento setup:upgrade
Processing configurations data from configuration file...
The following themes will be registered: frontend/Hyva/Elgentos
Do you want to continue [yes/no]?

With the change in this MR, we'll get this output from setup:db:status;

$ bin/magento setup:db:status
Themes are not up to date
Run 'setup:upgrade' to update your DB schema and data.

Since we rely on the output of setup:db:status to decide whether or not to run setup:upgrade in our deployment pipeline (to make near-zero downtime deployments possible), this is tripping us up from time to time.

This PR aims to add a validator to check whether there are theme changes, forcing setup:upgrade to run.

Thanks to @johnorourke for pointing this out.