* fix(deps): update kotlin to 2.3.0
* Cleanup - remove `datetime` compat version
* Fix several lint issues caused by the Kotlin compiler inference working better (checks in nullables, vars, etc.)
* Fix tests by removing mock in `File.readBytes`, it seems like it's no longer allowed. Using a tmp file works well enough.
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Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>
Co-authored-by: Benoit Marty <benoit@matrix.org>
Co-authored-by: Jorge Martín <jorgem@element.io>
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