chore(build): Add support for building with RHEL 9+ / Fedora 38+ / modern Podman alongside Docker / tested on Fedora 44

[rahst12]

Description

Podman / Fedora 44 / RHEL 9+ support for make test

NOTE: RedHat 8 was End of Life May 2024.

Docker CE is no longer installable or functional on Fedora 38+ and RHEL 9+ from the official
Docker repository. Podman (with podman-docker and podman-compose) is the supported
replacement on those platforms. This release makes the ./t runner and testutil compose
paths runtime-agnostic so that make test works with either Docker or Podman transparently.

Changes by area:

• testutil/runtime.go (new): central runtime detection; auto-detects whether Docker or
  Podman is in use (including podman-docker shims), sets DOCKER_HOST to the Podman socket
  so the Docker SDK can communicate with it, and exposes ContainerRuntime() and
  ContainerComposeCmdPrefix() helpers used everywhere else

• t/t.go and testutil/bulk.go: all hardcoded docker compose --compatibility
  invocations replaced with ContainerComposeCmdPrefix(); all docker logs, docker cp, and
  docker exec calls replaced with ContainerRuntime()

• contrib/Dockerfile: pre-creates all /data/zero*, /data/alpha*, /data/dg1, and
  /data/dg0.1 directories; Podman's crun OCI runtime does not auto-create a container's
  working_dir at startup (unlike Docker's runc), which left containers stuck in "Created"
  state

• t/Makefile: new install-deps-docker-linux-dnf target installs
  podman podman-docker podman-compose and enables the Podman socket instead of attempting the
  broken Docker CE install path on Fedora/RHEL

• t/scripts/check-deps-docker.sh: rewritten to detect and validate Podman on
  dnf-based systems instead of requiring Docker CE

• t/scripts/check-docker-available-memory.sh: reads /proc/meminfo directly on Linux
  (works for both Docker and Podman) rather than calling docker info

• Makefile (root): new $(DOCKER) variable falls back to podman when docker is
  absent, used for image build targets

• Fixed

  • fix(build): chain the jemalloc build recipe with && (was ;) so a failed compile no longer
    falls through to make install, and clear any stale /tmp/jemalloc-temp before rebuilding

Note: an earlier revision of this PR compiled the bundled jemalloc with --disable-cxx to
work around the std::__throw_bad_alloc build failure on GCC 16 / libstdc++ 16. That failure
was fixed upstream in #9740 (released in v25.4.0) by patching the jemalloc source, so this PR
no longer changes the configure flags. It now scopes to: Podman/make test infrastructure
support, multi-distro build dependencies (apt/dnf/pacman), and fail-fast hygiene in the
jemalloc recipe.

• Added

  • test: add contrib/smoke-test.sh to bring up a local zero+alpha and verify
    schema/mutation/query against a freshly built binary

• Changed

  • build: linux-dependency now auto-detects the package manager (apt/dnf/pacman) and installs the
    C/C++ toolchain + protobuf-compiler, so build prerequisites work on Fedora/RHEL and Arch in
    addition to Debian/Ubuntu

• Docs

  • docs(contributing): document building Dgraph on Fedora/RHEL

Checklist

• The PR title follows the
  Conventional Commits syntax, leading
  with fix:, feat:, chore:, ci:, etc.
• Code compiles correctly and linting (via trunk) passes locally
• Tests added for new functionality, or regression tests for bug fixes added as applicable
• [-] For public APIs, new features, etc., a PR on the
  docs repo staged and linked here. This process can
  be simplified by going to the public docs site and clicking the
  "Edit this page" button at the bottom of page(s) relevant to your changes. Ensure that you
  indicate in the PR that this is an unreleased feature so that it does not get merged into
  the main docs prematurely.

[rahst12]

I'm looking for feedback on the fedora 44 supports. What's needed to get this going?