Investiguate improvements to the follow endpoints

[loicmathieu]

Feature description

From the webserver we have two follow endpoints to follow and execution running, or execution logs.
Those use the queue so, in JDBC, they poll the database using a lock each 25ms!

We should revisit that as it causes unnecessary load on the database on the most used tables: queues.

Possible solutions:

1. poll the executions or the logs table directly, this can be problematic as those are indexed async (except executions in JDBC)
2. use a poll without locking and with a higher period: this means we would expose internal detail of the polling mechanism to the webserver