Internal #582: Remove utc_offset Dependency

[hawkfish]

pg_timezone_names.utc_offset changes over time
so tests should not rely on it. We were lucky for a while but our luck just ran out...

fixes: duckdblabs/duckdb-internal#582

[carlopi]

Thanks! Looks good to me.

Only though, this seems something we could benefit from having more dynamic tests, something like:

1. spawn postgres, popolate a table with pg_timezone_names(), save it in a postgres1.db file
2. spawn duckdb, popolate a table with pg_timezone_names(), save it in a duckdb.db file
3. spawn popolate a table with pg_timezone_names(), save it in a postgres2.db file
4. if postgres1.db and postgres2.db have different logical content, we are mid-change / bad luck, bail out
5. spawn duckdb, check postgres1.db and duckdb.db if they contain the same logical data
6. take a new timezone + sudo date --set "random date in the next couple of years", iterate a few times

Basically having tests where we aim to mimik postgres behaviour (until proven they do it wrong!)

But this requires some more infrastructure, for now I think we are good with the changes.

[hawkfish]

Thanks! Looks good to me.

Only though, this seems something we could benefit from having more dynamic tests, something like:

1. spawn postgres, popolate a table with pg_timezone_names(), save it in a postgres1.db file
2. spawn duckdb, popolate a table with pg_timezone_names(), save it in a duckdb.db file
3. spawn popolate a table with pg_timezone_names(), save it in a postgres2.db file
4. if postgres1.db and postgres2.db have different logical content, we are mid-change / bad luck, bail out
5. spawn duckdb, check postgres1.db and duckdb.db if they contain the same logical data
6. take a new timezone + sudo date --set "random date in the next couple of years", iterate a few times

Basically having tests where we aim to mimik postgres behaviour (until proven they do it wrong!)

But this requires some more infrastructure, for now I think we are good with the changes.

Thanks @carlopi - that's better than me sitting there diffing blocks in my editor(!) The only issue is that we track ICU a bit differently than PG (we have more zones) so we couldn't compare the data files directly, but some sort of outer join and filter would solve that I think.