Merge conflicts included:
* One setting being removed (branch had changed its type).
* One setting's description being changed (branch had changed its type).
* List of files in components/files was changed both upstream and on the
branch.
* Upstream had changed something in a file the branch deletes.
This PR aims to start addressing `ESM` design issues that have silenced errors we incorporated into groundcover `ESM` loading approaches.
- We move the resolution of `parentFileIndices` from `ESMStore` to `ESMReader` as suggested in a `TODO` comment.
- We improve a highly misleading comment which downplayed the significance of `parentFileIndices`.
- We document important preconditions.
- We move a user facing error message to the highest level and improve its context.
- We remove an inappropriate `setGlobalReaderList` method. We now pass this reader list into the method that requires it.
- We remove a thoroughly pointless optimisation of `Store<ESM::LandTexture>`'s construction that has unnecessarily depended on `getGlobalReaderList`.
There should be no functional changes for `master`, but this PR should remove an issue blocking PR #3208.
