RFR: 8324856: Serial: Move Generation::is_in to DefNewGeneration

[Albert Mingkun Yang]

On Mon, 29 Jan 2024 15:51:41 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

> Trivial moving code from superclass to subclass.

Thanks for review.

-------------

PR Comment: https://git.openjdk.org/jdk/pull/17616#issuecomment-1916349605