Merge #8371: [Qt] Add out-of-sync modal info layer
08827df [Qt] modalinfolayer: removed unused comments, renamed signal, code style overhaul (Jonas Schnelli)
d8b062e [Qt] only update "amount of blocks left" when the header chain is in-sync (Jonas Schnelli)
e3245b4 [Qt] add out-of-sync modal info layer (Jonas Schnelli)
e47052f [Qt] ClientModel add method to get the height of the header chain (Jonas Schnelli)
a001f18 [Qt] Always pass the numBlocksChanged signal for headers tip changed (Jonas Schnelli)
bd44a04 [Qt] make Out-Of-Sync warning icon clickable (Jonas Schnelli)
0904c3c [Refactor] refactor function that forms human readable text out of a timeoffset (Jonas Schnelli)