Limit session length

[marandaneto]

Right now session length is hardcoded to 24h

posthog-js/src/sessionid.ts

Line 13 in ec6fb94

const SESSION_LENGTH_LIMIT = 24 * 3600 * 1000 // 24 hours

We can probably make this much shorter by default (let's say 4 hours?) but also allow it to be set as a configuration.

Very long sessions may cause issues during the playback due to the amount of CPU and RAM consumed.

Tickets https://posthoghelp.zendesk.com/agent/tickets/11727

[marandaneto]

This could affect pricing so let's think before doing this change.
An option is to make it configurable and keep it 24h by default.