[Metric] Add ray metrics implementation

[zhongchun]

What do these changes do?

This pr adds ray metrics implementation which can be used when mars on ray. And we can use ray's metric backend to record and report metrics data to external system in this scenario.

We can use ray metrics as follows:

from mars.metric.api import init_metrics, Metrics

init_metrics({"metric": {"backend": "ray"}})
c = Metrics.counter("test_counter", "A test counter", ("service", "tenant"))
c.record(1)

g = Metrics.gauge("test_gauge", "A test gauge")
g.record(1)

m = Metrics.meter("test_meter")
m.record(1)

h = Metrics.histogram("test_histogram")
h.record(1)

Related issue number

Issue #2743

Check code requirements

• tests added / passed (if needed)
• Ensure all linting tests pass, see here for how to run them

[wjsi]

Need to add tests under Ray. Try use require_ray decorator to wrap ray-specific tests. Also rename RayMetric to RayMetricMixin to make things consistent.

[zhongchun]

Need to add tests under Ray. Try use require_ray decorator to wrap ray-specific tests. Also rename RayMetric to RayMetricMixin to make things consistent.

Thanks for your reminder. There are ray metrics tests in mars/metric/backends/ray/tests/test_ray_metric.py. I'll fix the name.

[wjsi]

Append a # pragma: no branch at the end of the line to avoid branch coverage report. What's more, it is recommended to use ray_metrics is None.

[zhongchun]

Ok. Thanks!

[wjsi]

Ditto.

[zhongchun]

I'll fix it.

[qinxuye]

LGTM

[wjsi]

LGTM