bpf: Track verifier register diagnostic events

Record material register and outgoing stack argument changes so diagnostics can
explain how a value reached its current type, bounds, or unreadable state.

Store old and new register types, scalar ranges, tnum value and mask, map and
BTF type identity, and basic operand metadata in the environment-owned
diagnostic event stream.

Record invalidations when packet data moves, references are released, or
borrowed references leave their protected region. Register-scoped history
starts at the latest matching modification and then shows later branch
outcomes.

Also record fixed stack spills and overwrites, and tag register fills from
stack so register-scoped history can follow value flow through spilled stack
slots.

The type_is_map_ptr() helper previously lived as a static function in
kernel/bpf/log.c since commit 0c95c9fdb696 ("bpf: emit map name in register
state if applicable and available"). Move it verbatim to
include/linux/bpf_verifier.h as a static inline, next to the other type
classifiers, so diagnostics.c can reuse it without duplicating the case list.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://patch.msgid.link/20260815064612.378577-6-memxor@gmail.com
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>

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