Gutenframe: Consider switching cache busting to a hash-based approach.

We currently bust the cache every day for the dotcom block editor scripts, to allow us fast updates in the case they're needed during this initial launch period. Once we're confident that can be reduced, we can investigate reducing the occurrence, or move to a [hash-based approach](https://href.li/?https://github.com/Automattic/jetpack/pull/12070#discussion_r277117371).

Start with the hash-based cache-busting discussion linked from Automattic/jetpack#12070 and inspect how the dotcom block editor scripts currently receive daily cache-busting values. Confirm the launch-period requirement before defining the change; done means a reviewed approach that reduces unnecessary busting while still allowing script updates to propagate reliably.

Written by the indexing model from the issue text.