Fix: wrong reference count after invalid `Map[key] = value`

[Wi1l-B0t]

Description

When set a value to map, The old value reference removed in Line 55 or the new key reference added in Line 57.

But if Line 60 throws a InvalidOperationException, the reference count will be wrong, because the ReferenceCounter has been updated, but the internal collection not.

https://github.com/neo-project/neo/blob/6c7f6c435e2fb308737b97cb1bc783c6a296bcc5/src/Neo.VM/Types/Map.cs#L52-L62

Type of change

• [ ] Optimization (the change is only an optimization)
• [ ] Style (the change is only a code style for better maintenance or standard purpose)
• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] This change requires a documentation update

Checklist:

• [x] My code follows the style guidelines of this project
• [x] I have performed a self-review of my code
• [x] I have commented my code, particularly in hard-to-understand areas
• [ ] I have made corresponding changes to the documentation
• [x] My changes generate no new warnings
• [x] I have added tests that prove my fix is effective or that my feature works
• [x] New and existing unit tests pass locally with my changes
• [ ] Any dependent changes have been merged and published in downstream modules