Supply language_id values to Neovim LSP API

Change logic so ALE's LSP implementation and the Neovim LSP client
retrieve the language_id for language clients at roughly the same time
via the same means. This makes ALE inform the language server what the
language for the language is for clients.

test/lsp/test_closing_documents.vader

@@ -37,24 +37,24 @@ After:
   runtime autoload/ale/lsp.vim
 
 Execute(No errors should be thrown if the connection is not initialized):
-  call ale#lsp#Register('command', '/foo', {})
+  call ale#lsp#Register('command', '/foo', '', {})
   call MarkDocumentOpened()
 
   call ale#engine#Cleanup(bufnr(''))
   AssertEqual [], g:message_list
 
 Execute(No messages should be sent if the document wasn't opened):
-  call ale#lsp#Register('command', '/foo', {})
+  call ale#lsp#Register('command', '/foo', '', {})
   call MarkAllConnectionsInitialized()
 
   call ale#engine#Cleanup(bufnr(''))
   AssertEqual [], g:message_list
 
 Execute(A message should be sent if the document was opened):
-  call ale#lsp#Register('command', '/foo', {})
+  call ale#lsp#Register('command', '/foo', 'lang', {})
   call MarkAllConnectionsInitialized()
 
-  call ale#lsp#OpenDocument('command:/foo', bufnr(''), 'lang')
+  call ale#lsp#OpenDocument('command:/foo', bufnr(''))
   call ale#engine#Cleanup(bufnr(''))
   " We should only send the message once.
   call ale#engine#Cleanup(bufnr(''))
@@ -78,10 +78,10 @@ Execute(A message should be sent if the document was opened):
   \ g:message_list
 
 Execute(A message should be sent if the document was opened for tsserver):
-  call ale#lsp#Register('command', '/foo', {})
+  call ale#lsp#Register('command', '/foo', 'lang', {})
   call ale#lsp#MarkConnectionAsTsserver('command:/foo')
 
-  call ale#lsp#OpenDocument('command:/foo', bufnr(''), 'lang')
+  call ale#lsp#OpenDocument('command:/foo', bufnr(''))
   call ale#engine#Cleanup(bufnr(''))
   " We should only send the message once.
   call ale#engine#Cleanup(bufnr(''))
@@ -94,12 +94,12 @@ Execute(A message should be sent if the document was opened for tsserver):
   \ g:message_list
 
 Execute(Re-opening and closing the documents should work):
-  call ale#lsp#Register('command', '/foo', {})
+  call ale#lsp#Register('command', '/foo', 'lang', {})
   call MarkAllConnectionsInitialized()
 
-  call ale#lsp#OpenDocument('command:/foo', bufnr(''), 'lang')
+  call ale#lsp#OpenDocument('command:/foo', bufnr(''))
   call ale#engine#Cleanup(bufnr(''))
-  call ale#lsp#OpenDocument('command:/foo', bufnr(''), 'lang')
+  call ale#lsp#OpenDocument('command:/foo', bufnr(''))
   call ale#engine#Cleanup(bufnr(''))
 
   AssertEqual
@@ -134,12 +134,12 @@ Execute(Re-opening and closing the documents should work):
   \ g:message_list
 
 Execute(Messages for closing documents should be sent to each server):
-  call ale#lsp#Register('command', '/foo', {})
-  call ale#lsp#Register('command', '/bar', {})
+  call ale#lsp#Register('command', '/foo', 'lang', {})
+  call ale#lsp#Register('command', '/bar', 'lang', {})
   call MarkAllConnectionsInitialized()
 
-  call ale#lsp#OpenDocument('command:/foo', bufnr(''), 'lang')
-  call ale#lsp#OpenDocument('command:/bar', bufnr(''), 'lang')
+  call ale#lsp#OpenDocument('command:/foo', bufnr(''))
+  call ale#lsp#OpenDocument('command:/bar', bufnr(''))
   call ale#engine#Cleanup(bufnr(''))
   " We should only send the message once.
   call ale#engine#Cleanup(bufnr(''))

test/lsp/test_did_save_event.vader

@@ -39,7 +39,7 @@ Before:
   let g:ale_linters = {'foobar': ['dummy_linter']}
 
   function! ale#lsp_linter#StartLSP(buffer, linter, Callback) abort
-    let g:conn_id = ale#lsp#Register('executable', '/foo/bar', {})
+    let g:conn_id = ale#lsp#Register('executable', '/foo/bar', 'foobar', {})
     call ale#lsp#MarkDocumentAsOpen(g:conn_id, a:buffer)
     let l:details = {
     \ 'command': 'foobar',

test/lsp/test_lsp_custom_request.vader

@@ -39,7 +39,7 @@ Before:
 
   " Replace the StartLSP function to mock an LSP linter
   function! ale#lsp_linter#StartLSP(buffer, linter, Callback) abort
-    let g:conn_id = ale#lsp#Register(g:executable_or_address, g:project_root, {})
+    let g:conn_id = ale#lsp#Register(g:executable_or_address, g:project_root, '', {})
     call ale#lsp#MarkDocumentAsOpen(g:conn_id, a:buffer)
     call ale#lsp#HandleMessage(g:conn_id, Encode({'method': 'initialize'}))
 

test/lsp/test_lsp_startup.vader

@@ -441,7 +441,7 @@ Execute(Deferred addresses should be handled correctly):
   call AssertInitSuccess('foo', 'localhost:1234', 'foobar', '/foo/bar', '', bufnr(''))
 
 Execute(Servers that have crashed should be restarted):
-  call ale#lsp#Register('foo', '/foo/bar', {})
+  call ale#lsp#Register('foo', '/foo/bar', '', {})
   call extend(ale#lsp#GetConnections()['foo:/foo/bar'], {'initialized': 1})
 
   " Starting the program again should reset initialized to `0`.

test/lsp/test_other_initialize_message_handling.vader

@@ -4,7 +4,7 @@ Before:
   let g:message_list = []
 
   " Register a fake connection and get it for tests.
-  call ale#lsp#Register('ale-fake-lsp-server', '/code', {})
+  call ale#lsp#Register('ale-fake-lsp-server', '/code', '', {})
   let b:conn = ale#lsp#GetConnections()['ale-fake-lsp-server:/code']
 
   function! ale#lsp#Send(conn_id, message) abort

test/lsp/test_update_config.vader

@@ -1,7 +1,7 @@
 Before:
   runtime autoload/ale/lsp.vim
 
-  let g:conn_id = ale#lsp#Register('executable', '/foo/bar', {})
+  let g:conn_id = ale#lsp#Register('executable', '/foo/bar', '', {})
 
   " Stub out this function, so we test updating configs.
   function! ale#lsp#Send(conn_id, message) abort