Problem:
The fromRanges field of the result of callHierarchy/outgoingCalls is
documented as being relative to the caller. Using
vim.lsp.buf.outgoing_calls() opened the qflist with an entry with the
callee's filename, but the caller's line number.
Solution:
Open the qflist with the callers file (the bufnr from the request),
rather than the callees (the uri from the resulting CallHierarchyItem)