The current script service has a script compilation limit for a one
minute window. This is set to a small default value of 15. Instead of
increasing that default value, this commit introduces a new setting 
that allows to configure a rate per time unit, so that the script service can deal with bursts better.

The new setting is named `script.max_compilations_rate`,
requires a nonnegative number and a positive time value.

The default is `75/5m`, which is equivalent to the existing 15 per minute.