`--override-crs` should rewrite the CRS in imported LAZ files

In #1057 I added the `--override-crs` flag to pointcloud imports. It avoids errors when tiles have different CRSes, and sets the CRS of the dataset in the `meta/` item. It doesn't actually change the CRS in the imported LAZ files though. It needs to, otherwise those LAZ files are not going to be useable with most software (or will require CRS override at usage time) We should: * use the reader's `override_srs` option in the existing PDAL conversion pipelines: https://pdal.io/en/stable/stages/readers.las.html#readers-las * force a PDAL conversion step even if not otherwise required, when this option is used.