Add page size info to tombstone

Now that Android devices can use 16k page size, it's important that we
know what configuration the device is in when see issues.

1) If the device is in 4k mode, we see nothing new.

2) If the device is in 16k mode, we see this line in the tombstones:

Page size: 16

3) If the device is in 4k mode, but was previous in 16k mode we see:

Has been in 16kb mode: yes

Test: atest debuggerd_test
Test: atest debuggerd_test with ro.misctrl.16kb_before="1"
Test: adb shell cat /data/tombstones/tombstone_00
Bug: 335247092
Change-Id: If7ca3b0954a01070ff413758296460ca1d023ca5