Pathway to getting encoding to `v1`

[tcharding]

v1.0.0 only does decoding. We would like to be able to do encoding as well now and its well overdue.

Proposed plan

1. Make current iter public Make iter module public #203
2. Port minimal public API to support encoding (keep iterators private)
3. Make encoding iterator public

Is there any benefit in doing a release for each step (i.e., v1.1.0 for (1), v1.2.0 for (2) etc)?

Before we can release any of this we/I will need to go through the API checklist and check we have everything new we expose correct.

[tcharding]

EDIT: Changed point (2) after leanings from rust-bitcoin/rust-bitcoin#5737 (reply in thread)

Another idea would be:

1. Polish master
2. semver trick the 1.0 API Copy the 1.0 stuff over to master
3. Release v0.4.0 and mark it as an RC like we did to the stabalizing crates in Release tracking PR: bitcoin-io 0.4.0-rc.0 rust-bitcoin#5461
4. Dowstream test it in bitcoin etc
5. Release v1.1 from master branch