treewide: Use Rust

This is:

- About 4x faster (~25ms to `-p` on my machine vs. ~100ms)
- About 6x lower in memory usage (~5MB vs. ~30MB)

This is more or less a 1:1 reimplementation, with only a few changes:

- contrib/09-timezone is gone. The script was never maintained by
  upstream, relies a lot on somewhat suspect parsing of gdbus/w/who
  output, and generally could use some love. No objection to something
  like this being in here in future, but it should avoid manual parsing
  of things like gdbus.
- --print-system-timezone is gone. As far as I know it was only used for
  that contrib script.
- --debug is now RUST_LOG=tzupdate=...
- The short name for --ip is now -i, not -a (...remind me why it was -a
  again?)
- IP-API does not support HTTPS freely, so remove it and only use
  services which do.
- Use HTTPS for worldtimeapi.
- FreeGeoIP now does a 301 to https://api.ipbase.com/v1/json/, so just
  go to there directly.
- Added services: reallyfreegeoip and ipwho.is.

Author: cdown

.gitignore

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+/target