Add PyrightSetPythonPath command in pyright config

The new command accepts a single path for a python executable that will
be used to reconfigure the pyright language server. This is useful to
change which python will be used by pyright without having to activate
the python environment beforehand. The act of finding which python
executable to use isn't handled here.

lua/lspconfig/server_configurations/pyright.lua

@@ -24,6 +24,17 @@ local function organize_imports()
   vim.lsp.buf.execute_command(params)
 end
 
+local function set_python_path(path)
+  local clients = vim.lsp.get_active_clients {
+    bufnr = vim.api.nvim_get_current_buf(),
+    name = 'pyright',
+  }
+  for _, client in ipairs(clients) do
+    client.config.settings = vim.tbl_deep_extend('force', client.config.settings, { python = { pythonPath = path } })
+    client.notify('workspace/didChangeConfiguration', { settings = nil })
+  end
+end
+
 return {
   default_config = {
     cmd = cmd,
@@ -45,6 +56,12 @@ return {
       organize_imports,
       description = 'Organize Imports',
     },
+    PyrightSetPythonPath = {
+      set_python_path,
+      description = 'Reconfigure pyright with the provided python path',
+      nargs = 1,
+      complete = 'file',
+    },
   },
   docs = {
     description = [[