Initialize properly timestamps at instanciation of WeatherUpdater

Description

Sometimes update of weather could not happen when tapping on the update button.

Technical details

We now initialize properly timestamps at instanciation of WeatherUpdater. Timestamps were boot persistent so they not correct after a reboot. I got rid off use of shared pref to maintain timestamps. We now maintain timestamps in RAM with regular variables.

Issues

e/backlog#7010 (closed)

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