[backport#15615] Add log output during initial header sync
Summary:
Add log output during initial header sync (Jonas Schnelli)
Pull request description:
The non debug log output is completely quiet during the header sync. I see two main reasons to add infos about the state of the initial header sync... * users may think the node did fail to start sync * it's a little complicate to check if your getting throttled during header sync (repeatedly calling `getchaintips` or similar)
Backport of Core PR15615
Test Plan:
ninja check check-functional
run bitcoind with a fresh datadir and see the new header sync log output
Reviewers: #bitcoin_abc, deadalnix
Reviewed By: #bitcoin_abc, deadalnix
Differential Revision: https://reviews.bitcoinabc.org/D7624