Monitor metric APIs

[zwmagic]

What type of PR is this?

Feature

What this PR does / why we need it?

It is hoped that Sermant will support Prometheus monitoring so that Sermant's core metrics as well as each plugin's custom metrics can be monitored through Grafana.

Which issue(s) this PR fixes？

Fixes #1445

Does this PR introduce a user-facing change?

No

Get Prometheus metric at http:// 127.0.0.1:47128/sermant/metrics

Checklist

• Make sure there is a GitHub_issue related with this PR before you start working on it.
• Make sure you have squashed your change to one single commit.
• GitHub Actions works fine in this PR.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 218 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
.../sermant/implement/service/metric/MeterMetric.java	0.00%	50 Missing ⚠️
...plement/service/metric/MeterMetricServiceImpl.java	0.00%	31 Missing ⚠️
...ervice/metric/api/DistributionStatisticConfig.java	0.00%	29 Missing ⚠️
.../java/io/sermant/core/service/metric/api/Tags.java	0.00%	19 Missing ⚠️
...o/sermant/implement/service/metric/MeterTimer.java	0.00%	15 Missing ⚠️
.../main/java/io/sermant/core/utils/ReflectUtils.java	0.00%	13 Missing ⚠️
...rmant/core/service/metric/config/MetricConfig.java	0.00%	10 Missing ⚠️
...o/sermant/implement/service/metric/MeterGauge.java	0.00%	9 Missing ⚠️
...sermant/implement/service/metric/MeterCounter.java	0.00%	8 Missing ⚠️
...sermant/implement/service/metric/MeterSummary.java	0.00%	8 Missing ⚠️
... and 7 more

Flag	Coverage Δ	Complexity Δ
unittests	43.77% <0.00%> (-0.33%)	182.00 <0.00> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ	Complexity Δ
...n/java/io/sermant/core/service/ServiceManager.java	9.23% <ø> (ø)	0.00 <0.00> (ø)
.../main/java/io/sermant/core/utils/SpiLoadUtils.java	0.00% <0.00%> (ø)	0.00 <0.00> (ø)
...va/io/sermant/core/service/metric/api/Counter.java	0.00% <0.00%> (ø)	0.00 <0.00> (?)
...va/io/sermant/core/service/metric/api/Summary.java	0.00% <0.00%> (ø)	0.00 <0.00> (?)
...java/io/sermant/core/service/metric/api/Gauge.java	0.00% <0.00%> (ø)	0.00 <0.00> (?)
...in/java/io/sermant/core/service/ServiceConfig.java	0.00% <0.00%> (ø)	0.00 <0.00> (ø)
...service/metric/handler/MetricHttpRouteHandler.java	0.00% <0.00%> (ø)	0.00 <0.00> (?)
...ic/prometheus/PrometheusMeterRegistryProvider.java	0.00% <0.00%> (ø)	0.00 <0.00> (?)
...sermant/implement/service/metric/MeterCounter.java	0.00% <0.00%> (ø)	0.00 <0.00> (?)
...sermant/implement/service/metric/MeterSummary.java	0.00% <0.00%> (ø)	0.00 <0.00> (?)
... and 8 more