fa927055dd refactor: Make m_last_notified_header private (MarcoFalke)
Pull request description:
Seems brittle to expose mutable fields public.
Fix it by making it private.
Fixes https://github.com/bitcoin/bitcoin/pull/30425#discussion_r1677633601
ACKs for top commit:
dergoegge:
utACK fa927055dd
Tree-SHA512: d9841c42571144ced0edeaa4bb1d96a177a011dca37c8342c66513477c37278602a1b88beb93068b94fc4443b1552c8fc9f98bcf0bda7d0fc101e61e90c33944