log: log lines collected by debug.zip seem to be truncated to 65K

It seems that log entries can be arbitrarily large, but when they're collected by the debug.zip (and I assume by the UI) through [this RPC](https://github.com/cockroachdb/cockroach/blob/ef7ab9bc810fd4be7755ebf8880e36ace9453f4b/pkg/cli/zip.go#L573) something seems to truncate them to 65KB each.
This is particularly unfortunate for query traces, which are a single entry (with many lines).

