It would be nice if you could replace a VCR with a ROP that is file based

[leftwo]

crucible/upstairs/src/volume.rs

Lines 1596 to 1598 in 4ec8152

	_ => {
	crucible_bail!(ReplaceRequestInvalid, "Cannot replace VCR")
	}

We don't need this for the product, but it would be nice if we could support VCR replacement
when the VCR has a ROP based on a file backend. Some test setups use this.