feat(build): Switch to docker hardened image

[Dav1dde]

See: getsentry/rfcs#157 (Rendered)

Switches from distroless to dhi. This is now possible because we no longer link against libstdc++ since relay-crash is gone.

└─ % llvm-readelf --needed-libs relay
NeededLibraries [
  ld-linux-x86-64.so.2
  libc.so.6
  libgcc_s.so.1
  libm.so.6
]

Another nice upside - ~13 MiB smaller:

REPOSITORY                TAG                                        IMAGE ID       CREATED          SIZE
ghcr.io/getsentry/relay   52824874f1c376153f43c04cb4924f63305ca489   9c24a95c0bda   22 minutes ago   83.8MB
ghcr.io/getsentry/relay   8421d6859682657eaa8cc183166cbf6e568eebd1   2529bda2f319   4 hours ago      96.4MB