chore: add insta snapshot example

[kormide]

An example for working with insta snapshot tests. Includes a macro that stamps a rust_test along with an executable rule to update snapshots in the source tree.

[kormide]

@illicitonion @UebelAndre

[kormide]

The CI failures are unclear to me. They don't appear to be caused by this example.

[illicitonion]

This generally looks reasonable (and useful!), but I'm not super sure of the value of this living in this repo... @UebelAndre any thoughts?

[kormide]

This generally looks reasonable (and useful!), but I'm not super sure of the value of this living in this repo... @UebelAndre any thoughts?

Yeah, it's a bit awkward that this solution is coupled to the nuances of insta. At some point I wanted to to do snapshot tests in rust and I couldn't find any examples. Searching rules_rust issues and examples was the first place I looked, so I figured it might go here.

If not, I'm happy to host it in an example repo of my own.

[kormide]

@alexeagle is there a home for this under aspect-build/bazel-examples?

[UebelAndre]

My initial thoughts on this are "is this demonstrating something unique that other rules examples do not?" and it seems like this is some handy rule but beyond that seems like a crate specific rule. I could see it becoming a crate_universe example but currently those in particular are more like integration tests that I don't think belong in examples (should instead be test/integration). Curious what @illicitonion thoughts are on the examples and if they should be cleaned up. If so then there's probably appetite for something like this.