Support for LSP/tsserver Code Actions (#3437)

* Added tsserver and LSP code action support.
* tsserver refactors support added.
* Handling special case when new text is added after new line symbol.
* ale#code_action#ApplyChanges simplified.
* Initial attempt on LSP Code Actions.
* workspace/executeCommand added.
* Some null checks added.
* Add last column to LSP Code Action message.
* Pass diagnostics to LSP code action.

Previously ApplyChanges code was applied from top-to-bottom that required 
extra parameters to track progress and there was bug. I have changed code
to bottom-to-top approach as that does not require those extra parameters
and solved the bug.

Tested with typescript-language-server and it is working.

test/test_code_action.vader

@@ -3,6 +3,9 @@ Before:
 
   let g:ale_enabled = 0
 
+  " Enable fix end-of-line as tests below expect that
+  set fixeol
+
   runtime autoload/ale/code_action.vim
   runtime autoload/ale/util.vim
 
@@ -211,6 +214,7 @@ Execute(End of file can be modified):
   \)
 
   AssertEqual g:test.text + [
+  \  '',
   \  'type A: string',
   \  'type B: number',
   \  '',