Add kernel info to compatibility.zip

Add kernel configs / version to verified_assembled_vendor_manifest.xml
so that the kernel of the incoming package can be checked against
the framework. Previously, the running kernel was used instead.

Bug: 111125947
Test: test_extract_kernel
Test: manual OTA on Pixel 3 from build:
      Android P (kernel version 4.9.96)
      to ToT build:
      device kernel version = (manually modified) framework requirement = latest,
      PRODUCT_OTA_ENFORCE_VINTF_KERNEL_REQUIREMENTS = true

Change-Id: Id524a58e94bdb6bba348ca461c9d33614ce451a9