Implement `submitpackage` back to v24?

[tcharding]

In #14 we added support for submitpackage for v28 and I claimed incorrectly that the method was new to v28.

Turns out it exists in the bitcoin-cli help output in v27 also and more confusingly running bitcoin-cli- help submitpackage against nodes as far back as v24 returns docs. Does this mean it exists and is functional but is undocumented or something else?

To close this issue the SubmitPackage type and accompanying code should be move out of types/src/v28/raw_transaction.rs and into the directory for the first version it is supported by Core.

[tnull]

I think this is also wrong (?): according to Core's release notes, it has been 'officially added' with v26, since when it's usable on mainnet (see bitcoin/bitcoin#27609). Note that it has been experimental since then, and is only really usable for most application since the introduction of TRUC transactions with v28, IIUC.

[tcharding]

Oh boy, so we cannot use bitcoin-cli help output as the SSOT for what is supported - that hurts. I guess that means for every version from v18 onwards, as we add support for new methods we have to check the release notes for fishy stuff like this. Not to worry, I did imagine we'd need to do that at some stage anyways.

Thanks man!

[apoelstra]

If doing this starts to feel like too much of a maintenance burden, please just fall back to the bitcoin-cli help output and maybe some "patches welcome" ability to override.

It is really really not our job to reverse-engineer Core's RPC protocol from natural text and tea leaves. And also -- I think that after 22(?) or so we shouldn't have to worry about this, because they did an overhaul of their RPC logic such that there are now functional tests between their help text and what their commands actually accept.

[tcharding]

Closed by #117, moved back to v26. Note the integration test is different for v26 to the one for v27 and v28