fix(ci): switch to upstream ps-http-sim from our fork (prisma#4983)

The upstream project has been revived since we forked it and has had
some improvements, including an official Docker image. Our fork stopped
compiling with the latest Go version leading to CI failures, so it's a
good opportunity to switch to the upstream.

docker/planetscale_proxy/Dockerfile

@@ -1,12 +1,14 @@
-FROM golang:1
+FROM ghcr.io/mattrobenolt/ps-http-sim:v0.0.9 AS planetscale-proxy
 
-RUN apt update && apt install netcat-openbsd -y
-RUN cd /go/src && git clone https://github.com/prisma/planetscale-proxy.git
-RUN cd /go/src/planetscale-proxy && go install .
+# ps-http-sim provides a barebones image with nothing but the static binary
+# but we also rely on netcat being present. Alpine provides it as part of busybox.
+FROM alpine:latest
 
-ENTRYPOINT /go/bin/ps-http-sim \
-  -http-addr=0.0.0.0 \
-  -http-port=8085 \
+COPY --from=planetscale-proxy /ps-http-sim /ps-http-sim
+
+ENTRYPOINT /ps-http-sim \
+  -listen-addr=0.0.0.0 \
+  -listen-port=8085 \
   -mysql-addr=$MYSQL_HOST \
   -mysql-port=$MYSQL_PORT \
   -mysql-idle-timeout=1s \