vim-patch:8.2.0114: info about sourced scripts is scattered

Problem:    Info about sourced scripts is scattered.
Solution:   Use scriptitem_T for info about a script, including s: variables.
            Drop ga_scripts.

7ebcba61b2

Co-authored-by: Bram Moolenaar <Bram@vim.org>

src/nvim/runtime.h

@@ -55,7 +55,16 @@ typedef enum {
   ESTACK_SCRIPT,
 } estack_arg_T;
 
-typedef struct scriptitem_S {
+/// Holds the hashtab with variables local to each sourced script.
+/// Each item holds a variable (nameless) that points to the dict_T.
+typedef struct {
+  ScopeDictDictItem sv_var;
+  dict_T sv_dict;
+} scriptvar_T;
+
+typedef struct {
+  scriptvar_T *sn_vars;         ///< stores s: variables for this script
+
   char *sn_name;
   bool sn_prof_on;              ///< true when script is/was profiled
   bool sn_pr_force;             ///< forceit: profile functions in this script