Add more packages to support practice exercises?

The Julia track is currently missing 53 unimplemented practice exercises. Mostly, these are just things we never got round to, or didn't much like, but several would be difficult with the current test runner.

I tentatively propose that we add two more packages:
- `TimeZones`, needed by multiple exercises (especially since Erik recently added new ones to `problem-specifications`).
- `Combinatorics`, which is certainly useful for Zebra Puzzle and probably others.

While I was digging around in `Project.toml`, I also noticed that the `[compat]` section specifies `julia = "1.7"` (I think this means that version or later). As 1.7 is long-since deprecated, I propose changing this to 1.10 (the current LTS version).

Because of worries about bloating the docker image even more than it is already, I tried a test build with these three changes. The image size increased by 12 MB - terrible for a more compact language, but only a 0.90% increase for Julia (see [previous issue](https://github.com/exercism/julia/issues/958)). I haven't yet tried making the changes separately, but my guess is that TimeZones is the big one (with data tables for every region), and Combinatorics is just a small bit of code.

Questions include:
- Is this worthwhile?
- How should we test changes before merging?

Slightly off-topic, but I also noticed that the `Manifest.toml` pins a few packages to specific versions (though most are free to use the latest compatible version). This file hasn't been updated since 2022, so it's something else to think about (non-urgently).