Cache and display build logs

[humphd]

Fixes #2535.

This adds a cache to the build log stream, so that when new clients connect, we start by sending the beginning of the log that they missed (if any). It also allows us to stream the previous build's log, so we can always display the last build that completed.

The basic idea is that when we create the stream for the build process, we also create a cache stream buffer, which we fill with the data from the build output. Then, whenever we need to send that data back again, we can get its contents and return. This also allows us to remember the previous build's log and send it to whoever wants it later on.

I have tested nothing in this PR (yolo!) and I'm not sure how to test this without running it on staging. This is just a draft to get things started.

[gitpod-io]

[Andrewnt219]

Can't say it works for sure because I cannot run the auto-deployment server, but the logic looks straightforward to me. As I understand, the server now additionally writes to the build.cache while streaming the new data. And on response, it writes the cache first before appending new data.

Some logic changes in the client but it should work just fine. The code refactoring is a nice addition 👍. Maybe we will need a date library down the road or just wait for Temporal.

[DukeManh]

Great work 👍 coding in the dark.

Build fail

[tpmai22]

I think it's good, I learned a lot.

[Andrewnt219]

LGTM🤞.

[humphd]

I'm not sure what else to do on this without actually merging it and testing live. @manekenpix I assume you would have to manually set this up if I merged? Is there a time that's good for us to try that, so I don't break staging?

[manekenpix]

@humphd I'll set up the autodeployment server later today (at 6ish) and launch telescope using this branch for testing.

[humphd]

Fixed a bunch of crashes @manekenpix found on staging, rebased and integrated the work that landed recently on the build log header. I think this is ready (again).

[humphd]

I missed a lock file fix that went in with @dbelokon's video changes. Rebased and updated.