[Tracking Issue] Reimplement MFS rather than band-aid it

MFS is a part of the Kubo codebase that is known to be fraught with issues and also an area where maintainers are weary to come in and make quick fixes. It's believed that the MFS implementation needs to be rethought rather than apply bandaids.

The purpose of this tracking issue is so can:
1. link issues that come in about MFS to it so there is good source material to consider when implementing MFS. (That can also be gleaned by searching for issues with the [topic/MFS label](https://github.com/ipfs/kubo/issues?q=is%3Aissue+label%3Atopic%2FMFS+)).
2. have a central place to communicate about MFS status. Ideally, interested parties can subscribe to this issue and be notified if development starts happening on it.

This ideally is a project that could write up a grant for and enable someone else to come in and develop since at the minimum this isn't a priority for Kubo maintainers in 2022.

Start by reviewing issues with the topic/MFS label and the existing discussion collected under this tracking issue. Identify the MFS problems that a reimplementation must address; done would require a new MFS implementation rather than isolated fixes, with its status communicated here.

Written by the indexing model from the issue text.