Multi-survivor support for SVM GC

[张同宝(井桐)]

Dear Graal developers,

Substrate VM is a great framework to generate executable native images for Java applications. Thank you for making it open-source.
We (Alibaba) are trying to use Substrate VM and native-image to speed up the startup of our cloud-based Java applications.

Meantime, we also found problems when running our applications using SVM.
The full GC occurred more frequently than the HotSpot VM because there are no object age and survivor spaces in the current SVM GC implementation.

We made some improvements to the SVM GC to address these problems, which can significantly decrease the full GC frequency.
We would like to contribute a patch to the community, including the multi-survivor support of SVM builtin GC to reduce the frequency of full GC.
We have tested this patch thoroughly in our production environment and are glad to contribute it to the Graal community.

Look forward to your response.

Thanks,
Tongbao Zhang