Drop support for Python 3.7 after v0.9.0

[auxten]

As pandas start to drop Python 3.7 from 2021.

• Pandas 2.0 with pyarrow backend support require at least Python 3.8.
• The memfd_create feature for #36 is also introduced in Python 3.8.

So I decided to drop support for Python 3.7 after v0.9.0. For Python 3.7 the last available chdb version is 0.9.0

Any feedback will be appreciated.