Make VM int parsing not use static global non-constant tables.

In anticipation of isolate-group code execution.

While there, made it skip leading zeros before doing length-based
choices for parsing.

Tested: Refactoring, not change in behavior.
Bug: https://dartbug.com/61030
Change-Id: I4b27b3b85b263c67fe0066eff85172a20f0fed5b
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/442680
Commit-Queue: Lasse Nielsen <[email protected]>
Reviewed-by: Martin Kustermann <[email protected]>
Reviewed-by: Alexander Aprelev <[email protected]>

Author: lrhn

sdk/lib/_internal/vm/lib/double_patch.dart

@@ -72,8 +72,7 @@ class double {
       } else if ((c | 0x20) == _e) {
         i++;
         if (i == end) return null;
-        // int._tryParseSmi treats its end argument as inclusive.
-        final int? expPart = int._tryParseSmi(str, i, end - 1);
+        final int? expPart = int._tryParseSmi(str, i, end);
         if (expPart == null) return null;
         exponent += expPart;
         break;