Add a new subcommand to workerd for making a Python snapshot

[hoodmane]

For now this only makes baseline snapshots but I'll extend it to make package snapshots when I need it.

[dom96]

We already have python-save-baseline-snapshot (

workerd/src/workerd/server/workerd.c++

Line 779 in dd3effd

.addOption({"python-save-baseline-snapshot"}, [this]() {

) for this which I think is the same as what you're adding here, right?

[dom96]

Ahh okay, you want a nicer command that doesn't require a config.