Improve release artifacts

[GCdePaula]

There are a few improvements to the node release artifacts. First, we should do #130, renaming the node binary to cartesi-rollups-prt-node.

Then we should make the following changes to the node artifacts:

• support both linux/amd64 and linux/arm64;
• make the substring "Linux" in the name lowercase (i.e. "linux");
• use amd64 instead of x86_64.

The result should be two artifacts:

1. targetlinux/amd64: cartesi-rollups-prt-node-0.1.0-rc.1_linux_amd64.tar.gz
2. target linux/arm64: cartesi-rollups-prt-node-0.1.0-rc.1_linux_arm64.tar.gz

We want to keep using sha256 checksum, so we need the analogous of these two binaries as well.

[guidanoli]

With PR #245, node assets now include the software version and target architecture (for now, AMD64 or ARM64).
It does not, however, include the target OS, in this case, Linux. Should we?
Moreover, do the Linux binaries work on macOS? If not, should we target macOS as well?
CC @endersonmaia

[endersonmaia]

It does not, however, include the target OS, in this case, Linux. Should we?

If we only support linux, I'm OK not having -linux- in the name for now.

When it's decided to support another OS, then we should put linux, darwin, freebsd and whatever we shall support.

[endersonmaia]

We want to keep using sha256 checksum, so we need the analogous of these two binaries as well.

GitHub Release is already providing the sha256 hashes as part of the release process.

See: https://github.blog/changelog/2025-06-03-releases-now-expose-digests-for-release-assets/