docs: Migrate oasis-node setup section, more commands

[matevz]

Part of https://github.com/oasisprotocol/docs/pull/399. This PR migrates a number of oasis-node commands previously described inside the general/manage-tokens/advanced/oasis-cli-tools section to this repository where they should probably be in the first place.

[matevz]

There are two sections referenced from the other parts of docs as I noticed:

• Setup section (mostly describing $TX_FLAGS and $ADDR used in node operators docs) is not in the CLI
• gen_cast_vote section which is currently missing in the CLI

We could remove other token management sections I guess, but these still exist in the current oasis-core master and 22.x branches right so why not document them?

[kostko]

Setup section (mostly describing $TX_FLAGS and $ADDR used in node operators docs) is not in the CLI

The node operator docs should be migrated to use the CLI as well because all of this is clunky as hell, but ok let's leave them for now.

gen_cast_vote section which is currently missing in the CLI

This should be easy to add to the CLI, but ok let's leave it for now.

We could remove other token management sections I guess, but these still exist in the current oasis-core master and 22.x branches right so why not document them?

Yes we should remove them. The reason is that we should be directing people to use the CLI instead and not having these in docs allows us to remove them from master at any point. Also the CLI already supports 22.x so we should push people to use it now not later.