Use XRPLF heavy runners

[Patel-Raj11]

Changes

• Use heavy / heavy-arm64 for Linux builds (inside the clio-ci container, matching build-and-test)
• Use macos15 for macOS arm64 builds
• Use windows runner for Windows builds; remove explicit MSVC environment setup (ilammy/msvc-dev-cmd)
• Replace setup-python + pip install with XRPLF/actions/prepare-runner
• Add Cleanup workspace step for the persistent macos15 runner
• Skip native-binaries on forks (matches build-and-test's pattern)

Still on GHA-hosted runners

• macOS Intel (macos-15-intel) — no XRPLF Intel runner available
• Linux s390x (ubuntu-latest) — QEMU setup needs privileged binfmt registration, which heavy doesn't allow.

[mathbunnyru]

We can and should still use heavy here

[Patel-Raj11]

@mathbunnyru I tried using heavy runners for s390x, but it keeps failing with the error seen in below mentioned run. After some back and forth with Claude, it seems that heavy runners are running in some sandbox/VM/namespace such that docker/setup-qemu-action is not working as intended.

https://github.com/XRPLF/mpt-crypto/actions/runs/24976270406/job/73128730834

Can you see if you can suggest something based on the error message? Or s390x is quite unique (it needs docker emulation) so can we keep using GHA runners?