Rake Task gitlab:backup:create to support CI Database

What does this MR do and why?

The rake tasks gitlab:backup:create and gitlab:backup:restore should include the decomposed databases (main, ci) in case that is configured.

Note: I am skipping the undercoverage tests, because it keeps complaining about the already broken and to be deprecated rake task gitlab:backup:db:restore. See the relevant issue here: #369150

Related Issue: #364292 (closed)

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