GetTimeMillis has multiple issues:
- It doesn't denote the underlying clock type
- It isn't type-safe
- It is used incorrectly in places that should use a steady clock
Fix all issues here.
> refactor, qt: Use std::chrono for MODEL_UPDATE_DELAY constant
https://github.com/bitcoin-core/gui/pull/517/commits/33d520ac538fcd6285fd958578f1bd26295592e4
> net: Use steady clock in InterruptibleRecv
> test: Use steady clock in index tests
See D14087 for why 30s in blockfilter_index_tests
> wallet: Use steady clock to measure scanning duration
> wallet: Use steady clock to calculate number of derive iterations
with `MillisecondsDouble` from core#26118
This is a backport of core#27405 and a partial backport of core-gui#517