Currently there are some confusions in net_processing:
* There is confusion between `-blocksonly mode` and `block-relay-only`,
so adjust all comments to use the same nomenclature.
* Whether to disconnect peers for providing invs/txs is implemented
differently. For example, it seems a bit confusing to disconnect
`block-relay-only` peers with `relay` permission when they send a tx
message, but not when they send an inv message. Also, keeping track of
their inv announcements seems both wasteful and confusing, as it does
nothing. This isn't possible in practice, as outbound connections do
not have permissions assigned, but sees fragile to rely on. Especially
in light of proposed changes to make that possible:
https://github.com/bitcoin/bitcoin/pull/17167
This is a backport of core#25156