* Disable aggregation bundling on `/sync` responses
A partial revert of #11478. This turns out to have had a significant CPU impact
on initial-sync handling. For now, let's disable it, until we find a more
efficient way of achieving this.
* Fix tests.
Co-authored-by: Patrick Cloke <patrickc@matrix.org>
Due to updates to MSC2675 this includes a few fixes:
* Include bundled aggregations for /sync.
* Do not include bundled aggregations for /initialSync and /events.
* Do not bundle aggregations for state events.
* Clarifies comments and variable names.