Fix dev mode when the same file is marked multiple times for hot deploy

[gsmet]

Better reviewed commit per commit.

Fixes #13722

Also changes the behavior for named persistence units (which is slightly related as we will then only produce the import.sql build item once).

/cc @Sanne I would need your blessing for the change of behavior in the second commit. My rationale is that there's a good chance you will not want to push the same import.sql for your additional named datasources.

[gsmet]

@geoand can you check the first commit?

[geoand]

First commit looks good!

[Sanne]

I'm ok with it if you feel strongly about it, but I'm not 100% persuaded that this is the right thing to do.

I agree that it's unlikely to be useful for the same import script to be imported by multiple PUs, but this same "oddness" has been areound for a long time in vanilla Hibernate as well.

So the difference in Quarkus is that we auto-configure the default one; the big question we don't really know is what if people prefer using a named PU (even though they have onlyone), and what's the experience when migrating from a default PU to a named PU ?

I'll approve as I have no strong opinion, but I'm a bit reserved that this will create confusion and maybe just requiring people to override each property explicitly is simpler to handle.

For sure will need some better explanation in migration docs.

[gsmet]

I /think/ it's the best thing to do but let's wait for someone to complain.

I dropped the second commit.