Use jdbc/initScript property instead of sql-maven-plugin

[lukaseder]

To simplify MCVE builds, we can use our own initScript property instead of the sql-maven-plugin. The property should only be used once 3.19 is no longer maintained, i.e. a few years from now, perhaps.

[lukaseder]

See this limitation:

• The code generation initScript property should be able to read from the file system jOOQ#16825

[lukaseder]

jOOQ/jOOQ#16825 is implemented. I'll ship 3.19.10 today, so this can be improved in the MCVE template as well.

[lukaseder]

Hm, no, let's not use the 3.19.10 feature yet. Users are likely downgrading jOOQ in the MCVE to make a reproducer using an older version. And then, they'll have to adapt the MCVE, which is annoying.