R1:078bf59f59b0

Compress Harbormaster build logs inline

Summary:
Ref T5822.

- After a log is closed, compress it if possible.
- Provide `bin/harbormaster archive-logs` to make it easier to change the storage format of logs.

Test Plan:
- Ran `bin/harbormaster archive-logs` on a bunch of logs, compressing and decompressing them without issues (same hashes, same decompressed size across multiple iterations).
- Ran new builds, verified logs were compressed after they closed.

Reviewers: chad

Reviewed By: chad…