entrybleed: restrict to the KPTI path, vote across passes

EntryBleed only works under KPTI, where the user page tables expose
entry_SYSCALL_64 as the one leakable kernel page. Without KPTI the whole
kernel is user-mapped, no page stands out, and the scan locks onto the
mapped region's left edge -- a base one offset too low. The paper defers
that case to the general prefetch attack, so decline it (DISP_ABSENT) and
leave it to the shipped prefetch scan rather than emit a wrong base. This
removes the now-unused start_rodata column and the non-KPTI code, comments,
and emit branch.

On the KPTI path, take the majority base over several passes instead of
requiring every pass to agree, so an occasional noisy pass is outvoted
rather than failing the probe and misreporting a vulnerable host.

Also fix five openSUSE rows whose fingerprints lacked the version string
and add a few Alpine builds.

Author: bcoles