If, due to invalidation / reconsideration of blocks, the previous best header is no longer valid / guaranteed to be the most-work header in our block-index not known to be invalid, recalculate it.
Declared in <validation.h>
[[requires_capability(0x7ff37ba95dd8), requires_capability(0x7ff375ddc768), requires_capability(0x7ff37e1a6038), requires_capability(0x7ff375a97ea8)]]
void
RecalculateBestHeader();