[ci] drop ubuntu 18.04 build test

Fix remaining golangci-lint errors

Add s3.max_idle_conns to example config file

Upgrade to go 1.24.2

Remove github release workflow

I will revert to producing the github release binaries manually
for now, so I can create binaries that run on OS releases older
than the currently-supported github-hosted runners.

Upgrade github.com/mostynb/go-grpc-compression to avoid decompression…

… bomb DoS

mostynb/go-grpc-compression#27

Build container image with clang-17 on arm64

Go fmt

Test /metrics with basic-auth and mTLS

Upgrade to go 1.20.1