Problem:
`vim.lsp.buf.definition`/`vim.lsp.buf.declaration` use the same underlying code
via `get_locations`, whereas `vim.lsp.buf.reference` does not. This is because
`buf.reference` does not perform a jump when there is only one item.
Solution:
In #38510, I simplified the jump logic using `:cfirst`, so they can now share
code more easily. Additionally, this PR enables `buf.definition` to display the
corresponding qflist name.
f9e068117b