aws_core: NestedStack tags cannot override parent stack tags in constructor

### Describe the bug

In this python code snippet:
```
app = aws_cdk.App()

stack1 = aws_cdk.Stack(app, "stack1")
tags = aws_cdk.Tags.of(stack1)
tags.add("foo", "bar")

stack2 = aws_cdk.NestedStack(stack1, "stack2")
tags = aws_cdk.Tags.of(stack2)
tags.add("foo", "zap", priority=2000)
```

The nested stack has tag `"foo": "bar"`.

### Expected Behavior

I expected `stack2` to have tag `"foo":"zap"` but it has tag `"foo":"bar"` inherited from the parent stack. Similarly, removing a tag that was added in the parent stack does not work, but adding a new ones does.

### Current Behavior

The inherited parent stack's tags cannot be modified by the nested stack.

### Reproduction Steps

```
import aws_cdk

app = aws_cdk.App()

stack1 = aws_cdk.Stack(app, "stack1")
tags = aws_cdk.Tags.of(stack1)
tags.add("foo", "bar")

stack2 = aws_cdk.NestedStack(stack1, "stack2")
tags = aws_cdk.Tags.of(stack2)
tags.add("foo", "zap", priority=2000)

app.synth()
```

Observe that `stack2` in the resulting cloudformation template has tag `"foo":"bar"`.

### Possible Solution

If this is expected behaviour I feel it should at least be documented (unless I missed that documentation somewhere).

### Additional Information/Context

_No response_

### CDK CLI Version

2.150.0 (build 3f93027)

### Framework Version

2.149.0

### Node.js Version

v20.12.1

### OS

Mac os X 14.5

### Language

Python

### Language Version

Python 3.10.11

### Other information

_No response_

Start with the Tags.of and NestedStack entry points and reproduce the behavior with app.synth() using the Python example. Trace how parent tags are inherited and how priority-based overrides or removals are handled, then add a regression test showing the synthesized nested-stack tags match the expected result.

Written by the indexing model from the issue text.