Split VABC into two .mk files

1. android_t_baseline.mk enables baseline features, such as io_uring,
   userspace merge, etc. But sets compression method to none. T
   launching devices should include this. It also moves snapuserd from
   vendor_ramdisk to init_boot
2. To add compression, set PRODUCT_VIRTUAL_AB_COMPRESSION_METHOD to
   gz/brotli

Test: th
Bug: 219841787

Change-Id: I6ae4d951b0a64f142acd4c152ce96375d47ecf74