The base finish metric is not set on clean exit of extractor

[AbdulrahmanAlshehri]

The below finish metric in BaseMetrics is never set during an extractor run. Requiring manually setting it to populate the metric. Is this intended to be the case?

python-extractor-utils/cognite/extractorutils/metrics.py

Lines 123 to 125 in 955ff6a

	self.finish = Gauge(
	f"{extractor_name}_finish_time", "Timestamp (seconds) of then the extractor last finished cleanly"
	)

If not, I can contribute to resolving this.