read item contents by `bufnr` instead of reading file by path

[eatgrass]

  local fd = assert(uv.fs_open(filename, "r", 438))

the filename might not be an valid file path, for example, the jdtls could return something like this jdt://contents/commons-collections4-4.4.jar/org.apache.commons.collections4.list/AbstractLinkedList.class?=b

it causes an error

stack traceback:
        [C]: in function 'assert'
        ....local/share/nvim/lazy/trouble.nvim/lua/trouble/util.lua:150: in function 'process_item'
        ....local/share/nvim/lazy/trouble.nvim/lua/trouble/util.lua:193: in function 'locations_to_items'
        ...are/nvim/lazy/trouble.nvim/lua/trouble/providers/lsp.lua:44: in function 'handler'
        ...are/nvim/lazy/trouble.nvim/lua/trouble/providers/lsp.lua:9: in function 'handler'
        ...w/Cellar/neovim/0.9.0/share/nvim/runtime/lua/vim/lsp.lua:1394: in function ''
        vim/_editor.lua: in function <vim/_editor.lua:0>

[folke]

That was actually an optimization so we don't need to load the buffer to get those lines. It made a huge difference in performance.

Can you change the impl so that it only does that when filename is an uri and not a file?

[folke]

thanks!

[eatgrass]

I am glad to contribute to this great plugin