Select applicable positions for lsp_ext methods more leniently (#32272)

Closes https://github.com/zed-industries/zed/issues/27238

Release Notes:

- Fixed `editor::SwitchSourceHeader` and
`editor::ExpandMacroRecursively` not working with text selections
fa02bd71c3Kirill Bulatov committed on 6/6/2025, 10:47:20 PM· committed by GitHubparent6d95fd9
4 files changedLine totals unavailable