Package solana-fullnode as a Linux snap

[mvines]

We'd like a way to easily distribute (and automatically update) solana-fullnode as widely as possible. Currently Linux users must have the full rust/cargo toolchain installed which is a barrier to entry, and makes #307 and #364 a little tougher than ideal (there should be no need to build solana-fullnode again when deploying it to a testnet or for CI testing.

Snaps seam to fit the bill nicely: https://snapcraft.io/
We can have nightly updates for a testnet setup, multiple release channels, and snaps can be installed explicitly/manually for CI testing.

Before proceeding further, we should confirm that CUDA is workable from within the confined environment of a snap. https://github.com/anonymouse64/cuda-samples-snap seems to imply this is possible.

• Basic snap infra
• CUDA snap support
• Document snap usage in README

[garious]

🥇