fix(ConvertType): Read dbtype in createConnectionParams and remove safeguard

[provokateurin]

Summary

Fixes #45257
Unforked version of #48666.
While testing I also found that #39242 read the hostname wrong which never worked.

I tested it successfully like this (make sure to have pdo_pgsql enabled):

docker run --rm --network=host --env POSTGRES_PASSWORD=postgres postgres:17
./occ maintenance:install --admin-pass admin
./occ db:convert-type --all-apps --password=postgres -- pgsql postgres localhost postgres
rm data/owncloud.db

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)

[provokateurin]

/backport to stable31

[provokateurin]

/backport to stable30

[provokateurin]

/backport to stable29

[nfebe]

Are the any auto tests for this?

[provokateurin]

Are the any auto tests for this?

No unfortunately not, as changing the DB inside the tests is not a good idea. I still want to add a test for it later though, but will have to see in what form.