Replace `StdIntMap` with `std::vector<int>`.

Change-Id: I877f3a8b363807cf96c66ba978c6c6cc6bd0688e
Reviewed-on: https://code-review.googlesource.com/c/re2/+/60010
Reviewed-by: Justin Lebar <jlebar@google.com>
Reviewed-by: Paul Wankadia <junyer@google.com>
2 files changed