**What type of PR is this?**
Other
**What does this PR do? Why is it needed?**
This pull request removes `NUMBER_OF_COLUMNS` and
`MAX_CELLS_IN_EXTENDED_MATRIX` configuration.
**Other notes for review**
Please read commit by commit, with commit messages.
**Acknowledgements**
- [x] I have read
[CONTRIBUTING.md](https://github.com/prysmaticlabs/prysm/blob/develop/CONTRIBUTING.md).
- [x] I have included a uniquely named [changelog fragment
file](https://github.com/prysmaticlabs/prysm/blob/develop/CONTRIBUTING.md#maintaining-changelogmd).
- [x] I have added a description to this PR with sufficient context for
reviewers to understand this PR.
* Fixed metadata extraction on Windows by correctly splitting file paths
* `TestExtractFileMetadata`: Refactor a bit.
---------
Co-authored-by: Manu NALEPA <enalepa@offchainlabs.com>
* `reconstructSaveBroadcastDataColumnSidecars`: Use the `s.columnIndicesToSample` instead of recoding its content.
ddd
* Rename `custodyColumns` ==> `columnIndicesToSample`.
* `DataColumnStorage.Save`: Remove wrong godoc.
* Implement `receiveDataColumnSidecars` and transform `receiveDataColumnSidecar` as a subcase of the plural version.
* `dataColumnSubscriber`: Add godoc and remove only once used variable.
* `processDataColumnSidecarsFromExecution`: Use single flight directly in the function.
So the caller does not have any more the responsability to deal with multiple simultaneous calls.
* `processDataColumnSidecarsFromReconstruction`: Guard against a single flight.
In `dataColumnSubscriber`, trig in parallel `processDataColumnSidecarsFromReconstruction` and `processDataColumnSidecarsFromExecution`.
Stop when the first of them is successful.
* `processDataColumnSidecarsFromExecution`: Use `receiveDataColumnSidecars` instead of `receiveDataColumnSidecar`.
* Implement and use `broadcastAndReceiveUnseenDataColumnSidecars`.
* Add changelog.
* Fix James' comment.
* Fix James' comment.
* `processDataColumnSidecarsFromReconstruction`: Log reconstruction duration.
