Eastern 66

Fixes

• Handle activity creation failures in spawn_instance (#458)
• Repeat Payment API calls on timeout errors (#473)
• Close async generators created by Executors on Golem shutdown (#482)

Minor changes

• Align logs datetime format with yagna - add milliseconds and a TZ offset (#463)

Updates and fixes to the examples

• Remove unneeded constants from the simple-service-poc example (#462)
• Fix import path to Service class in the hello-service example (#471)
• Replace NamedTemporaryFile usage in yacat example (#488)
• Add default value to yacat keyspace (#490)

Integration test updates

• Make goth runs compatible with yagna 0.7 (#470)
• Use dynamic stable branch in goth nightly (#480)