Fix DB2/400 schema generation on 5.3.x

[fredericDelaporte]

Fix #3438

Replace #3439.

That the commits from there, cherry-picked on 5.3.x with another one from #3450 allowing building 5.3.x.

[bahusoid]

Why new PR?

You can rebase existing PR on to 5.3.x branch with:

git rebase  --onto upstream/5.3.x upstream/master

[fredericDelaporte]

To avoid force pushing on the initial contributor remote. Many are confused by forced pushes.
And also, to have the choice between targeting master or 5.3.x by leaving intact the branch based on master.

[hazzik]

Please see my comments here: #3439 (comment) and here: #3438 (comment)

[hazzik]

We should either:

• Restore previous behavior for DB2400Dialect, eg, throwing NotSupportedException;
• Implement proper metadata for DB2400Dialect;
• Do nothing, and abandon this PR advising user to check the configuration, eg setting hbm2ddl.keywords to none or removing it altogether.

[shessane]

I hope you will go with the solution : Implement proper metadata for DB2400Dialect.

It would be sad not to take advantage of the advantages of the new implem just because of a column name. Let me share with you a better implementation.

[bahusoid]

I hope you will go with the solution : Implement proper metadata for DB2400Dialect.

We need to fix regression in 5.3.x branch and the safest way to go here is to restore 5.2.x behavior for DB2400Dialect. Proper metadata handling can be added to master branch later. Feel free to provide PR with proper metadata handling.

[fredericDelaporte]

The async regen fails due to these NuGet warnings treated as error, NU190x.

[bahusoid]

genarateasync yml doesn't see unmerged changes but it works. Tested in my branch: https://github.com/bahusoid/nhibernate-core/actions/runs/7014939230