16k: core: Add flag to make AOSP page size agnostic

The new boolean flag will be PRODUCT_PAGE_SIZE_AGNOSTIC.

When PRODUCT_PAGE_SIZE_AGNOSTIC is true:

- AOSP will use getpagesize() to retrieve the page size.
- The flag `TARGET_MAX_PAGE_SIZE_SUPPORTED` has to be equals to `65536`.
- AOSP will be able to use 4k/16k page size Linux kernels

When PRODUCT_PAGE_SIZE_AGNOSTIC is false:

- AOSP will only support 4k page size kernels.

Test: source build/envsetup.sh
      lunch aosp_raven_64-userdebug
      get_build_var TARGET_PAGE_SIZE_AGNOSTIC
      get_build_var PRODUCT_MAX_PAGE_SIZE_SUPPORTED
      65536

      source build/envsetup.sh
      lunch aosp_raven_64-userdebug
      build/make/core/config.mk:414: error: TARGET_MAX_PAGE_SIZE_SUPPORTED has to be 65536 to support page size agnostic.
      10:32:55 dumpvars failed with: exit status 1

Bug: 289419664
Change-Id: If8fc243a3e2cad77414a53a29805c7b6d349d4dd