saw-remote-api: Add --version command-line option

[RyanGlScott]

Just as the saw binary features a --version command-line option, the saw-remote-api binary should also include a --version option. This would be especially useful for the saw-remote-api Docker image (which is distributed separately from the saw Docker image), where it is otherwise indirect to determine what version is being used.

See also GaloisInc/cryptol#1815.

[sauclovian-g]

This turns out to be a headache because argo handles the command line, and while it lets the application add options to subcommands, it doesn't allow adding top-level options. So we can do saw-remote-api stdio --version relatively easy, but doing it properly requires API-breaking changes in argo.

Furthermore, the way the version information is generated in the build makes it only accessible to the saw executable. Getting it to saw-remote-api requires either a bunch of duplication or a bunch of reorganization, so we probably shouldn't try to get it into the immediately pending release.

[sauclovian-g]

(See GaloisInc/argo#218 in argo.)