CI: Publish reports to Github Actions

[nomeata]

This publishes our various reports to https://dfinity.github.io/motoko/. So far, only for master (github action doesn’t support PR deployments like netlify would).

[github-actions]

Comparing from 61883e8 to 054a46e:
The produced WebAssembly code seems to be completely unchanged.

[nomeata]

I thought maybe I can fix #2568 without waiting for anyone.

To boot, this PR creates a new derivation that combines all our “build reports” in one tree. This is a mild regression for what we had in hydra (there, you still could look at one report even though another might have failed), but probably ok.

Next I wanted to add a github action step that publishes that to a netlify page at https://motoko-builds.netlify.app/. But I stopped following that track because I need to be repo admin to configure secrets used by the build, but more importantly, it seems I use a netlify Personal Access Token which would give anyone with commit permissions on this repo the ability to control any of my netlify. So maybe netlify isn’t great either, at least not in this mode.

We could use Github Pages if we don’t mind a gh-pages branch polluting our repo. I’ll explore this once I can change the repo settings again.

[ggreif]

Why not upload to an asset canister on the IC?

[nomeata]

Heh, interesting idea. And we'd get bragging rights if we start using the IC before it's used for the official dfinity.org web page :-)

Technically not too hard: create a key, load it up with a few ICPs, put it into the GitHub actions secrets (if small enough), write tool to upload a directory to an asset canister (script around dfx or dedicated tools or see if it exists; fleek maybe), upload after push and put URL into a PR comment or so.

Intuitively I'd use one canister per deploy, with very short freezing time, and leave it to canister depletion and deletion to clean up old canisters. But I fear our cost model (with I think 10¢ per canister installation) discourages such many-canister models.

So we could use a single such canister, and deal with rotating out old builds ourselves.

Or start maybe with just hosting latest master anyways.

[nomeata]

Ok, deploy to github action works:

• https://dfinity.github.io/motoko/
• https://dfinity.github.io/motoko/flamegraphs/

Maybe start with this?

[ggreif]

LGTM! Modulo the debug code... Some links give 404 errors, but we can check that later.