ci: reduce size of Rust interop-test image

By using a multi-stage docker build, a distroless base image and a release build, we can get the size of the Rust interop test down to 50MB. Previously, the image would be around 500MB. A debug build image would still have ~400MB. The release build slows down our interop build step by about 1min 20s. That however is only because we don't currently seem to utilize the caches that from what I understand should work on self-hosted runners. I opted #3925 for that.

Resolves: #3881.

Pull-Request: #3926.
(cherry picked from commit 0bc724a)

interop-tests/Dockerfile

@@ -1,5 +1,11 @@
 # syntax=docker/dockerfile:1.5-labs
-FROM rust:1.67.0
+FROM rust:1.67.0 as builder
+
+# Install zlib as long as libp2p-websocket requires it: https://github.com/paritytech/soketto/issues/72
+RUN apt-get update && \
+    apt-get download zlib1g && \
+    mkdir /dpkg && \
+    for deb in *.deb; do dpkg --extract $deb /dpkg || exit 10; done
 
 # Setup protoc. TODO this breaks reproducibility and uses an old version of protoc.
 # In the future protobuf generated files will be checked in, so we can remove this
@@ -11,10 +17,13 @@ WORKDIR /workspace
 ADD . .
 RUN --mount=type=cache,target=./target \
     --mount=type=cache,target=/usr/local/cargo/registry \
-    cargo build --package interop-tests
+    cargo build --release --package interop-tests
 
 RUN --mount=type=cache,target=./target \
-    mv ./target/debug/ping /usr/local/bin/testplan
+    mv ./target/release/ping /usr/local/bin/testplan
 
+FROM gcr.io/distroless/cc
+COPY --from=builder /usr/local/bin/testplan /usr/local/bin/testplan
+COPY --from=builder /dpkg /
 ENV RUST_BACKTRACE=1
 ENTRYPOINT ["testplan"]