Document paper wallet usage for key generation

[mvines]

Similar to #7084, we need some documentation around using the paper wallet for key generation from an offline system that never touched the internet/etc.

[jstarry]

Off the top of my head this includes keypair generation and recovery using solana-keygen and inputting keypairs using seed phrases in our CLI tools. Anything else?

[mvines]

Yep, that please how to delegate stake with the paper wallet. I think that'll cover it for 0.21

[mvines]

I guess this issue could be folded into #7084...

[jstarry]

Yeah lots of overlap but I think it's fine to knock this one out to get the groundwork laid out for #7084. Question though... where do we want the docs to live?

How about a new section in the sidebar of the book called "Paper Wallet Usage" under "Running an Archiver"

[jstarry]

And then some links from the other sections to this new section with "Using a paper wallet?" call to actions?

[mvines]

sg. Just "Papet Wallet" as the section title seems sufficient but 🤷‍♂, we can better nit pick once there's some content in place

[jstarry]

Need a way to output the pubkey from a seed phrase without writing the keypair file.

Two options:

1. Add --ask-seed-phrase to solana-keygen pubkey
2. Add --no-outfile to solana-keygen recover