vim-patch:8.2.2070: can't get the exit value in VimLeave(Pre) autocommands (#13981)

Problem:    Can't get the exit value in VimLeave or VimLeavePre autocommands.
Solution:   Add v:exiting like in Neovim. (Yegappan Lakshmanan, closes vim/vim#7395)
f0068c5154

Rearrange VimVarIndex enums and vimvars[] entries to sync with  Vim.

N/A patches for version.c:

vim-patch:8.2.2535: MS-Windows: cannot run all vim9 tests

Problem:    MS-Windows: cannot run all vim9 tests.
Solution:   Make test_vim9 target work.
723ef5db98

src/nvim/eval.h

@@ -105,7 +105,6 @@ typedef enum {
     VV_DYING,
     VV_EXCEPTION,
     VV_THROWPOINT,
-    VV_STDERR,
     VV_REG,
     VV_CMDBANG,
     VV_INSERTMODE,
@@ -140,13 +139,9 @@ typedef enum {
     VV_OPTION_OLD,
     VV_OPTION_TYPE,
     VV_ERRORS,
-    VV_MSGPACK_TYPES,
-    VV_EVENT,
     VV_FALSE,
     VV_TRUE,
     VV_NULL,
-    VV__NULL_LIST,  // List with NULL value. For test purposes only.
-    VV__NULL_DICT,  // Dictionary with NULL value. For test purposes only.
     VV_VIM_DID_ENTER,
     VV_TESTING,
     VV_TYPE_NUMBER,
@@ -156,10 +151,16 @@ typedef enum {
     VV_TYPE_DICT,
     VV_TYPE_FLOAT,
     VV_TYPE_BOOL,
+    VV_EVENT,
     VV_ECHOSPACE,
-    VV_EXITING,
-    VV_LUA,
     VV_ARGV,
+    VV_EXITING,
+    // Neovim
+    VV_STDERR,
+    VV_MSGPACK_TYPES,
+    VV__NULL_LIST,  // List with NULL value. For test purposes only.
+    VV__NULL_DICT,  // Dictionary with NULL value. For test purposes only.
+    VV_LUA,
 } VimVarIndex;
 
 /// All recognized msgpack types