Since it's only used for transactions, there's no need to pass in an inv
type.

Backport of core PR18044.

Since thie PR is Segwit related, there is not much left.
Full commits:

• https://github.com/bitcoin/bitcoin/pull/18044/commits/60f0acda713e7b9dc188aef54ef93981a93f4e44
• https://github.com/bitcoin/bitcoin/pull/18044/commits/dd78d1d641178b473ab1156b71a837b9e686792b

Only the CInv equality operator in messages.py is relevant:

• https://github.com/bitcoin/bitcoin/pull/18044/commits/9a5392fdf67f1c5c90f52d3cdb3dea4f35d1609f