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)
Problem:
Cursor-position `vim.lsp.buf.code_action()` requests include all diagnostics on the current line, so unrelated same-line diagnostics affect the returned actions.
Solution:
Filter same-line diagnostics to the cursor position for cursor-position requests.
Problem:
`test/functional/plugin/lsp_spec.lua` had grown into a large catch-all file that mixed core LSP client lifecycle coverage, `vim.lsp.buf.*` behavior, and `vim.lsp.util.*` behavior in one place.
Solution:
Split the large tests into more focused test files without changing test coverage or intended behavior.
After this change, `lsp_spec.lua` is more focused on core LSP client/config/dynamic-registration behavior.
