App stuck when setting max pool size to 1 and using validation/update schema generation

[DavideD]

Follows quarkus#33776

Extracting the info needed for schema generation is a blocking operation

This seems to work fine when the max pool size is bigger than 1, but it will block the app when using validate or update schema generation options.

A quick way to test this is via SchemaUpdateMySqlTestBase after updating the configuration of the test with:

configuration.setProperty( Settings.POOL_SIZE, "1" );