Support multi-period intervals in throttling

[robhudson]

This pull request enhances the throttling functionality to support multi-period intervals, such as 5/30s, 10/5m, and 100/2h. Previously, the throttling implementation only allowed single-period intervals (e.g., 5/s, 100/d), which limited the granularity and flexibility of rate limits.

The new implementation expands the allowed syntax for throttle rates to accommodate use cases requiring multi-unit periods, making it easier to define more precise rate limits.

Motivation

While single-period intervals work for many scenarios, they lack flexibility for more complex use cases. For example:

• Higher granularity: A rate like 20/5m (20 requests every 5 minutes) cannot be expressed with the current system.
• Short-term bursts: Rates like 50/2h allow finer control over bursts without spanning a full day.

[vitalik]

Thank you