ui: show header pre-synchronization progress

Summary:
This concludes backport of core#25717
https://github.com/bitcoin/bitcoin/pull/25717/commits/3add23454624c4c79c9eebc060b6fbed4e3131a7

Depends on D15170

Test Plan:
With a fresh data dir:
ninja && src/qt/bitcoin-qt -printtoconsole

Check that the header presync status in the GUI (status bar and modal overlay) is updated and matches the status in the console.

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D15172