CI tasks `check-compiles` and `build` could use better names

## What problem does this solve or what need does it fill?

As mentioned by @BD103 [on the discord](https://discord.com/channels/691052431525675048/692572690833473578/1253116136145551441):
> `build` runs `cargo test` for the entire workspace, while `check-compiles` runs `cargo build` for all crates, examples, benchmarks, compile fail tests, etc.

The current names for these CI tasks aren't very accurate, and could use better ones.

## What solution would you like?

Better names! I'm not too particular on what they *should* be named, but perhaps:
- `build` -> `cargo test`
- `check-compiles` -> `cargo build`

So it's more obvious what exactly these tasks are doing.

Search the CI configuration for the `build` and `check-compiles` task definitions and references. Confirm what commands each task runs, rename the tasks to accurately describe them, update all references, and verify the CI configuration remains valid.

Written by the indexing model from the issue text.