refactor: sink metrics

[fuyufjh]

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What's changed and what's your intention?

Background

In other places (such as source), the usage of metrics is generally as follows:

• Inside SourceMetrics, there is a pair of MetricsVec instead of actual Metrics.
• Only when it comes to the specific working struct, build the actual Metrics from MetricsVec with particular labels.

While, on the sink side, SinkMetrics directly consist of a collection of Metrics.

What's in this PR

• Refactor SinkMetrics from a set of Metrics to a set of MetricVec
• Introduce a GLOBAL_SINK_METRICS
• Move the real Metrics into separated places:
  • SinkWriterMetrics for general sink metrics
  • LogWriterMetrics
  • LogReaderMetrics
  • Iceberg sink related metrics are in multiple places. See iceberg/mod.rs for details

This will also resolve the issue discussed at #17812 (comment), because it follows the standard pattern of #14838.

Follow-ups

• The metrics labels were a bit messy. I'd like to do a bit refactoring on them in future PR.

Checklist

• I have written necessary rustdoc comments
• I have added necessary unit tests and integration tests
• I have added test labels as necessary. See details.
• I have added fuzzing tests or opened an issue to track them. (Optional, recommended for new SQL features Sqlsmith: Sql feature generation #7934).
• My PR contains breaking changes. (If it deprecates some features, please create a tracking issue to remove them in the future).
• All checks passed in ./risedev check (or alias, ./risedev c)
• My PR changes performance-critical code. (Please run macro/micro-benchmarks and show the results.)

• My PR contains critical fixes that are necessary to be merged into the latest release. (Please check out the details)

Documentation

• My PR needs documentation updates. (Please use the Release note section below to summarize the impact on users)

Release note

If this PR includes changes that directly affect users or other significant modifications relevant to the community, kindly draft a release note to provide a concise summary of these changes. Please prioritize highlighting the impact these changes will have on users.

[wenym1]

Rest LGTM!

[wenym1]

Any reason to erase the connector label?

We can get the connector label easily from self.sink, which can be supported by implementing the following method for Sinkimpl

impl SinkImpl {
    pub fn sink_name(&self) -> &'static str {
        fn get_sink_name<S: Sink>(_sink: &S) -> &'static str {
            S::SINK_NAME
        }

        dispatch_sink!(self, sink, get_sink_name(&**sink))
    }
}

[fuyufjh]

Can do. I was thinking that, for LogWriterMetrics, it's supposed to be unaware of the log reader i.e. the actual Sink implementation.

Also, the sink_name is here, which I think is enough for users.