feat(lsp): improve LSP doc hover rendering #30695

Problem:
- Some servers like LuaLS add unwanted blank lines after multiline
  `@param` description.
- List items do not wrap nicely.

Solution:
- When rendering the LSP doc hover, remove blank lines in each `@param`
  or `@return`.
  - But ensure exactly one empty line before each.
- Set 'breakindent'.

test/functional/plugin/lsp/utils_spec.lua

@@ -83,7 +83,62 @@ describe('vim.lsp.util', function()
     end)
   end)
 
-  describe('normalize_markdown', function()
+  it('convert_input_to_markdown_lines', function()
+    local r = exec_lua(function()
+      local hover_data = {
+        kind = 'markdown',
+        value = '```lua\nfunction vim.api.nvim_buf_attach(buffer: integer, send_buffer: boolean, opts: vim.api.keyset.buf_attach)\n  -> boolean\n```\n\n---\n\n Activates buffer-update events. Example:\n\n\n\n ```lua\n events = {}\n vim.api.nvim_buf_attach(0, false, {\n   on_lines = function(...)\n     table.insert(events, {...})\n   end,\n })\n ```\n\n\n @see `nvim_buf_detach()`\n @see `api-buffer-updates-lua`\n@*param* `buffer` — Buffer handle, or 0 for current buffer\n\n\n\n@*param* `send_buffer` — True if whole buffer.\n Else the first notification will be `nvim_buf_changedtick_event`.\n\n\n@*param* `opts` — Optional parameters.\n\n - on_lines: Lua callback. Args:\n   - the string "lines"\n   - buffer handle\n   - b:changedtick\n@*return* — False if foo;\n\n otherwise True.\n\n@see foo\n@see bar\n\n',
+      }
+      return vim.lsp.util.convert_input_to_markdown_lines(hover_data)
+    end)
+    local expected = {
+      '```lua',
+      'function vim.api.nvim_buf_attach(buffer: integer, send_buffer: boolean, opts: vim.api.keyset.buf_attach)',
+      '  -> boolean',
+      '```',
+      '',
+      '---',
+      '',
+      ' Activates buffer-update events. Example:',
+      '',
+      '',
+      '',
+      ' ```lua',
+      ' events = {}',
+      ' vim.api.nvim_buf_attach(0, false, {',
+      '   on_lines = function(...)',
+      '     table.insert(events, {...})',
+      '   end,',
+      ' })',
+      ' ```',
+      '',
+      '',
+      ' @see `nvim_buf_detach()`',
+      ' @see `api-buffer-updates-lua`',
+      '',
+      -- For each @param/@return: #30695
+      --  - Separate each by one empty line.
+      --  - Remove all other blank lines.
+      '@*param* `buffer` — Buffer handle, or 0 for current buffer',
+      '',
+      '@*param* `send_buffer` — True if whole buffer.',
+      ' Else the first notification will be `nvim_buf_changedtick_event`.',
+      '',
+      '@*param* `opts` — Optional parameters.',
+      ' - on_lines: Lua callback. Args:',
+      '   - the string "lines"',
+      '   - buffer handle',
+      '   - b:changedtick',
+      '',
+      '@*return* — False if foo;',
+      ' otherwise True.',
+      '@see foo',
+      '@see bar',
+    }
+    eq(expected, r)
+  end)
+
+  describe('_normalize_markdown', function()
     it('collapses consecutive blank lines', function()
       local result = exec_lua(function()
         local lines = {