Tracking: Migrate to snapshot-based integration testing APIs

[rami3l]

Borrowing from Cargo's previous effort, this proposal tries to integrate a new testing DSL for better overall dev experience.

The idea is to make use of your IDE (or CLI, if you prefer) to update snapshots directly, instead of writing your expectations by hand:

I have a more ambitious goal of removing dependency injections altogether, but we must start from somewhere, so here it is.

Implementation History

• refactor(test): add new APIs for easier snapshot testing #4334
• style(test): clarify uses of snapbox::str![] #4342
• test(cli-self-upd): migrate to .expect() APIs #4343
• test(cli-exact): migrate to .expect() APIs #4352
• test(cli-inst-interactive): migrate to .expect() APIs #4353
• test(cli-paths): migrate to .expect() APIs #4354
• test(cli-misc): migrate to .expect() APIs #4363
• test(cli-rustup): migrate to .expect() APIs #4365
• test(cli-v1): migrate to .expect() APIs #4366
• test(cli-v2): migrate to .expect() APIs #4367
• test: finish migration to .expect() APIs #4376