WIP: change librustzcash dependency to track main

[dannasessha]

WIP, doesn't build!

fixes #79

This currently resolves to 3f5ba8de4823921092ab52a3e22e2516154f69b1, though it will dynamically point to the most recent commit in the main branch from https://github.com/zcash/librustzcash/

See #79 for details

[zancas]

Treat the following as an hypothesis to refine-and-or-test:

I propose:

• the 1 or 2 dependencies that are most closely intertwined with our current development are frequently manually inspected and re-pinned (including validation of passing CI, and inspection of commit messages and freshly-merged PRs)
• all other dependencies are pinned to latest main
• all of these dependencies:
  • https://github.com/zcash/orchard
  • https://github.com/zcash/zcash/tree/master/src/rust
  • https://github.com/zcash/librustzcash are "All Activity" "Watched"

I am currently watching "All Activity" on the three implied repos.. which might be too much noise... are they're tools available in github that could provide us with more nuanced insights into the evolution of these projects?

[AloeareV]

I'm hesitant to track main because of things like this, if we track main, any time librustzcash introduces a breaking change it breaks old versions of zecwalletlitelib. I think a regular update to latest-commit-at-present is a much better pattern, it would be great if we could automate that.

[dannasessha]

My own thought went like this.

This repo's dev could track main of librustzcash. This repo's releases (main) could have pinned commits, thereby making it so that releases would theoretically remain static and not break.

If we're working on dev and something breaks due to an update at librustzcash that's good to see quickly.

If we find we are not able to track their main on our dev because things break too much, alright, but that was the idea.

[zancas]

What's our latest policy WRT this?