Jack Grigg

This PR has now been blocking parts of `zcashd` deprecation for almost 4 months. I'm going to do the rebase myself and open a new PR.

> Zingo Labs reconsidered its strategy and significantly reallocated resources with the April 30th release of Zashi. > > I have done my best to make my position clear and...

As I said above, I've already picked this up myself, due to its necessity for zcashd deprecation. I'm currently on PTO though and not working on it until at least...

[Force-pushed](https://github.com/zcash/librustzcash/compare/8e66e0d952240ea304251fe78873a19a97f30770..d33ec1d5c0f0d34150691ca25ea90df47fcc42da) to clean up the commit history; no changes to @teor2345's changes, just regrouping them (and squashing some of the fixes into the original commits that didn't make sense to...

[Force-pushed](https://github.com/zcash/librustzcash/compare/d33ec1d5c0f0d34150691ca25ea90df47fcc42da..9dbdf1880e6a47f071d821aac48fd9d9cb1d78a8) to GitHub-linkify an imported source link in a commit message.

And somehow I managed to click two wrong buttons in a row 🤦

[Force-pushed](https://github.com/zcash/librustzcash/compare/9dbdf1880e6a47f071d821aac48fd9d9cb1d78a8..b201c1012e2332543f66636f830974ec38815904) to clean up the feature flagging in the build script, and add C `#ifdef`s to prevent some warnings.

[Rebased on current `main`](https://github.com/zcash/librustzcash/compare/b201c1012e2332543f66636f830974ec38815904..be16706e326a63165660e38a32b7b1b9eebdf06d). I will rebase this PR again once #1357 merges.

[Rebased on `main`](https://github.com/zcash/librustzcash/compare/be16706e326a63165660e38a32b7b1b9eebdf06d..ed22417ade401b2e98ffcb3a165a666336fc7fd1) to fix merge conflicts after #1357 was merged.

[Force-pushed](https://github.com/zcash/librustzcash/compare/ed22417ade401b2e98ffcb3a165a666336fc7fd1..6571aa980b0dff722d84317361844c30eea036be) to move the new minimal-form compression methods into the new submodule from #1357.