Migrate from java.time to kotlinx-datetime

[westnordost]

A further step to make the core part of StreetComplete platform independent (#1892), usages of java.time classes should be replaced with kotlinx-datetime. I have had a cursory look at v0.4.0 so far and it looks stable enough now, though some convenience functions are missing.

Steps to do

• add kotlinx-datetime as dependency
• Ctrl+F for usages of java.time in the project
• replace usages with equivalent classes from kotlinx-datetime
• (you'll notice, a lot of convenience functions are missing, so add those as extension functions to util/ktx/*.kt instead of littering the code with unwieldy constructs)

Note There is no 100% guarantee that every use case java.time is used in StreetComplete can be covered with kotlinx-datetime 0.4.0, after all it is still marked as "experimental" and I have had only a cursory look. But it looks quite complete by now.

[sumanabhi]

hey @westnordost, I want to pick this up. if it is still in the Unassigned stage.

[westnordost]

It is not assigned. Thank you! Or well, @matkoniecz assigned it to you now :-)

[westnordost]

I'll just unassign you in case someone else would like to do this. It can be re-assigned when you or someone else actually starts to work on it.