patch 8.2.0154: reallocating the list of scripts is inefficient

Problem:    Reallocating the list of scripts is inefficient.
Solution:   Instead of using a growarray of scriptitem_T, store pointers and
            allocate each scriptitem_T separately.  Also avoids that the
            growarray pointers change when sourcing a new script.
diff --git a/src/vim9compile.c b/src/vim9compile.c
index 9f273c5..6690622 100644
--- a/src/vim9compile.c
+++ b/src/vim9compile.c
@@ -1401,7 +1401,7 @@
 {
     hashtab_T	    *ht;
     dictitem_T	    *di;
-    scriptitem_T    *si = &SCRIPT_ITEM(sid);
+    scriptitem_T    *si = SCRIPT_ITEM(sid);
     int		    idx;
 
     // First look the name up in the hashtable.
@@ -1433,7 +1433,7 @@
     imported_T *
 find_imported(char_u *name, cctx_T *cctx)
 {
-    scriptitem_T    *si = &SCRIPT_ITEM(current_sctx.sc_sid);
+    scriptitem_T    *si = SCRIPT_ITEM(current_sctx.sc_sid);
     int		    idx;
 
     if (cctx != NULL)
@@ -1462,7 +1462,7 @@
     static int
 compile_load_scriptvar(cctx_T *cctx, char_u *name)
 {
-    scriptitem_T    *si = &SCRIPT_ITEM(current_sctx.sc_sid);
+    scriptitem_T    *si = SCRIPT_ITEM(current_sctx.sc_sid);
     int		    idx = get_script_item_idx(current_sctx.sc_sid, name, FALSE);
     imported_T	    *import;