### Motivation
After add label for prometheus metric by #2650, it will cause prometheus metric format check failed when no label specified for a statsLogger. The metric list as follow.
```
replication_bookkeeper_client_bookkeeper_client_bookie_watcher_NEW_ENSEMBLE_TIME{success="false",quantile="0.9999", } NaN
```

### Modification
1. add label empty check for `PrometheusTextFormatUtil`
2. add label scope check test cover
3. add prometheus metric regex pattern check in test case

Reviewers: lipenghui <penghui@apache.org>, Andrey Yegorov <None>, Matteo Merli <mmerli@apache.org>, Jia Zhai <zhaijia@apache.org>, Addison Higham <None>, Enrico Olivelli <eolivelli@gmail.com>

This closes #2718 from hangc0276/chenhang/fix_bookeeper_metric_bug and squashes the following commits:

8590704 [hangc0276] format code
a6942d4 [chenhang] fix prometheus metric provider bug and add test to cover label scope and metric format check
bb8b1e0 [Andrey Yegorov] Include gradle files into the source artifact for releases, exclude site2/**
732b6cf [Andrey Yegorov] [maven-release-plugin] prepare for next development iteration
b0d9f10 [Andrey Yegorov] [maven-release-plugin] prepare branch branch-4.14
8dc108b [Matteo Merli] y
73e22ca [Don Inghram] ISSUE2620: RocksDB log path configurable
034ef85 [Shoothzj] Fix logger member not correct; (#2605)
b824a60 [hangc0276] fix always select the same region set bug for RegionAwareEnsemblePlacementPolicy (#2658)
683ad45 [Matteo Merli] Allow to attach labels to metrics (#2650)
8091096 [Matteo Merli] Allow to bypass journal for writes (#2401)
63867a9 [Matteo Merli] Impose a memory limit on the bookie journal (#2710)
87579b0 [Matteo Merli] Read entry error should print lastAddConfirmed in the log (#2707)

### Motivation
After add label for prometheus metric by #2650, it will cause prometheus metric format check failed when no label specified for a statsLogger. The metric list as follow.
```
replication_bookkeeper_client_bookkeeper_client_bookie_watcher_NEW_ENSEMBLE_TIME{success="false",quantile="0.9999", } NaN
```

### Modification
1. add label empty check for `PrometheusTextFormatUtil`
2. add label scope check test cover
3. add prometheus metric regex pattern check in test case

Reviewers: lipenghui <penghui@apache.org>, Andrey Yegorov <None>, Matteo Merli <mmerli@apache.org>, Jia Zhai <zhaijia@apache.org>, Addison Higham <None>, Enrico Olivelli <eolivelli@gmail.com>

This closes #2718 from hangc0276/chenhang/fix_bookeeper_metric_bug and squashes the following commits:

8590704 [hangc0276] format code
a6942d4 [chenhang] fix prometheus metric provider bug and add test to cover label scope and metric format check
bb8b1e0 [Andrey Yegorov] Include gradle files into the source artifact for releases, exclude site2/**
732b6cf [Andrey Yegorov] [maven-release-plugin] prepare for next development iteration
b0d9f10 [Andrey Yegorov] [maven-release-plugin] prepare branch branch-4.14
8dc108b [Matteo Merli] y
73e22ca [Don Inghram] ISSUE2620: RocksDB log path configurable
034ef85 [Shoothzj] Fix logger member not correct; (#2605)
b824a60 [hangc0276] fix always select the same region set bug for RegionAwareEnsemblePlacementPolicy (#2658)
683ad45 [Matteo Merli] Allow to attach labels to metrics (#2650)
8091096 [Matteo Merli] Allow to bypass journal for writes (#2401)
63867a9 [Matteo Merli] Impose a memory limit on the bookie journal (#2710)
87579b0 [Matteo Merli] Read entry error should print lastAddConfirmed in the log (#2707)

### Motivation
After add label for prometheus metric by apache#2650, it will cause prometheus metric format check failed when no label specified for a statsLogger. The metric list as follow.
```
replication_bookkeeper_client_bookkeeper_client_bookie_watcher_NEW_ENSEMBLE_TIME{success="false",quantile="0.9999", } NaN
```

### Modification
1. add label empty check for `PrometheusTextFormatUtil`
2. add label scope check test cover
3. add prometheus metric regex pattern check in test case

Reviewers: lipenghui <penghui@apache.org>, Andrey Yegorov <None>, Matteo Merli <mmerli@apache.org>, Jia Zhai <zhaijia@apache.org>, Addison Higham <None>, Enrico Olivelli <eolivelli@gmail.com>

This closes apache#2718 from hangc0276/chenhang/fix_bookeeper_metric_bug and squashes the following commits:

8590704 [hangc0276] format code
a6942d4 [chenhang] fix prometheus metric provider bug and add test to cover label scope and metric format check
bb8b1e0 [Andrey Yegorov] Include gradle files into the source artifact for releases, exclude site2/**
732b6cf [Andrey Yegorov] [maven-release-plugin] prepare for next development iteration
b0d9f10 [Andrey Yegorov] [maven-release-plugin] prepare branch branch-4.14
8dc108b [Matteo Merli] y
73e22ca [Don Inghram] ISSUE2620: RocksDB log path configurable
034ef85 [Shoothzj] Fix logger member not correct; (apache#2605)
b824a60 [hangc0276] fix always select the same region set bug for RegionAwareEnsemblePlacementPolicy (apache#2658)
683ad45 [Matteo Merli] Allow to attach labels to metrics (apache#2650)
8091096 [Matteo Merli] Allow to bypass journal for writes (apache#2401)
63867a9 [Matteo Merli] Impose a memory limit on the bookie journal (apache#2710)
87579b0 [Matteo Merli] Read entry error should print lastAddConfirmed in the log (apache#2707)