Bundled Proposals

This is a hypothetical feature that have been discussed on a few occasions.

It could be useful for multiple proposals to be enacted together or not at all. Here are some use cases:

* Two protocol parameters from different groups are needed to be updated together atomically, however separate groups will impose separate voting thresholds and potentially might cause SPOs vote on a parameter that they normally would not be required to vote on (eg. one parameter is from a security group while another is not)
* Two unrelated proposal types must be enacted together, eg a `ParameterUpdate` is enacted only if `HardForkInitiation` was enacted

The issue names no files, tests, or entry points. Start by clarifying the design for atomically enacting multiple proposals, including voting thresholds and supported proposal combinations, then locate the proposal-enactment implementation. Done should include an agreed specification and tests covering the stated use cases.

Written by the indexing model from the issue text.