CloudWatchMetricsPublisher: Allow specifying custom, constant value dimensions

### Describe the feature

Add option in CloudWatchMetricsPublisher to specify a custom dimension with constant value.

### Use Case

I would like to record AWS SDK metrics per ECS task ID and per AWS service.

The `MetricCollection` does not contain ECS task id as a metric, so it can't be used as dimension. Currently there does not seem to be evident way of how to achieve this.

### Proposed Solution

Something like this:

```
CloudWatchMetricsPublisher
.builder()
.dimensions(List.of(ConstantMetric.create("TaskId", "constant value"), CoreMetric.SERVICE_ID))
```

### Other Information

_No response_

### Acknowledgements

- [ ] I may be able to implement this feature request
- [ ] This feature might incur a breaking change

### AWS Java SDK version used

2.17.275

### JDK version used

11.0.12

### Operating System and version

macOS