[WIP] Fix database sync

[koppor]

Improves the NOTIFY and LISTEN for PostgreSQL database (to get content)

Removes MySQL/MariaDB and Oracle support (due to high maintenance effort).

Mandatory checks

• Change in CHANGELOG.md described in a way that is understandable for the average user (if applicable)
• Tests created for changes (if applicable)
• Manually tested changed features in running JabRef (always required)
• Screenshots added in PR description (for UI changes)
• Checked developer's documentation: Is the information available and up to date? If not, I outlined it in this pull request.
• Checked documentation: Is the information available and up to date? If not, I created an issue at https://github.com/JabRef/user-documentation/issues or, even better, I submitted a pull request to the documentation repository.

[github-actions]

Your code currently does not meet JabRef's code guidelines.
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[Siedlerchr]

I have experience with liquibase, we use it at work.they offer a gralde plugin https://contribute.liquibase.com/extensions-integrations/directory/integration-docs/gradle/

[Siedlerchr]

https://forum.liquibase.org/t/adding-liquibase-to-an-existing-project/6076

[github-actions]

You modified Markdown (*.md) files and did not meet JabRef's rules for consistently formatted Markdown files.
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You can check the detailed error output by navigating to your pull request, selecting the tab "Checks", section "Tests" (on the left), subsection "Markdown".

[github-actions]

The build of this PR is available at https://builds.jabref.org/pull/11879/merge.