<!-- The PR description should answer 2 important questions: -->
### What
Update Rust to
[1.81.0](https://blog.rust-lang.org/2024/09/05/Rust-1.81.0.html).
### How
Update `rust-toolchain.yaml` and Dockerfiles
V3_GIT_ORIGIN_REV_ID: 8a1fe694caaded7a12220d2460e66009f969227a
### What
Upgrade to the latest version of Rust.
### How
I modified `rust-toolchain.toml` and ran `cargo update`.
V3_GIT_ORIGIN_REV_ID: 5fe675ee5dc568cd24de542c826ffd2d355f90ff
<!-- The PR description should answer 2 important questions: -->
### What
Upgrade to [Rust
1.80.0](https://blog.rust-lang.org/2024/07/25/Rust-1.80.0.html)
### How
Update `rust-toolchain.yaml` and Dockerfiles, fix warnings.
V3_GIT_ORIGIN_REV_ID: ba797e1aba6b9623a921734473a6b70a2a38c8b7
<!-- The PR description should answer 2 (maybe 3) important questions:
-->
### What
We've had our CI mixed between Github and Buildkite for a while, it's
time to commit. First step is moving the "tests" step to Github Actions.
<!-- What is this PR trying to accomplish (and why, if it's not
obvious)? -->
<!-- Consider: do we need to add a changelog entry? -->
### How
This PR:
- Moves the `test` step to Github Actions
- Creates a new `custom_connector.Dockerfile` which builds custom
connector only, more quickly.
- Changes the metadata tests to use `localhost` instead of their Docker
internal names (ie `custom_connector` or `postgres_connector`) - this is
because the tests are being run from outside Docker now
- Removes the `test` Buildkite step
It does not:
- Remove the code coverage or benchmarks steps from Buildkite
- Tidy up `justfile` or Dockerfiles
<!-- How is it trying to accomplish it (what are the implementation
steps)? -->
---------
Co-authored-by: Philip Lykke Carlsen <plcplc@gmail.com>
V3_GIT_ORIGIN_REV_ID: a67534ebc1634a24b48d2620c45003221852e199
