Fix error when downloading multiple jdbc drivers

[davidecavestro]

The databaseDriverUrl config property is a string potentially defining a comma-separated list of urls.
It is splitted and iterated on every single url, download the jdbc driver jar and detect a proper file name for it (among other things).
Unfortunately the filename detection throws a StringIndexOutOfBoundsException when the databaseDriverUrl config property has multiple urls (i.e. https://jdbc.postgresql.org/download/postgresql-42.2.20.jar,https://repo1.maven.org/maven2/com/oracle/database/jdbc/ojdbc11/21.1.0.0/ojdbc11-21.1.0.0.jar).

It probably meant to use the substring from the last index of the "/" separator to the end of the url,
but it uses the position from the whole databaseDriverUrl property (unsplitted).

This fix proposes to get the last index of the "/" separator from the currently processed driver url
in order to compute the jar file name, so trying to follow the intention of the author.

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[cniweb]

@prospero238 or @r2liquibase When does this continue? We need the update urgently too!