Only send LSP config updates when the dict changes

Each LSP connection now stores its configuration dictionary. It is
initially empty (`{}`) and is updated each time the LSP connection is
started. When a change is detected, the workspace/didChangeConfiguration
message is sent to the LSP servers with the updated configuration.

autoload/ale/lsp_linter.vim

@@ -201,13 +201,6 @@ function! ale#lsp_linter#StartLSP(buffer, linter) abort
     endif
 
     let l:config = ale#lsp_linter#GetConfig(a:buffer, a:linter)
-
-    if !empty(l:config)
-        " set LSP configuration options (workspace/didChangeConfiguration)
-        let l:config_message = ale#lsp#message#DidChangeConfiguration(a:buffer, l:config)
-        call ale#lsp#Send(l:conn_id, l:config_message)
-    endif
-
     let l:language_id = ale#util#GetFunction(a:linter.language_callback)(a:buffer)
 
     let l:details = {
@@ -218,6 +211,8 @@ function! ale#lsp_linter#StartLSP(buffer, linter) abort
     \   'language_id': l:language_id,
     \}
 
+    call ale#lsp#UpdateConfig(l:conn_id, a:buffer, l:config)
+
     if ale#lsp#OpenDocument(l:conn_id, a:buffer, l:language_id)
         if g:ale_history_enabled && !empty(l:command)
             call ale#history#Add(a:buffer, 'started', l:conn_id, l:command)