Allow clients to configure log history subscriptions

[bmingles]

Jsapi clients currently receive the entire log history when connecting to a core server. This probably makes sense on initial connection, but it can be problematic in cases where a user has cleared their logs and refreshed the page. There are other use cases such as the vscode-deephaven extension where having better control of the logging behavior would be helpful. Specifically, it would be nice to be able to configure how historical logging is provided as part of connecting / subscribing to logs.

[bmingles]

@mofojed this is the ticket we discussed earlier today for vscode extension log subscriptions.