add prometheus integration.

[JaredTan95]

support #2489

• Exposed prometheus API: /prometheus in Apollo-ConfigService, Apollo-Adminservice,Apollo-Portal modules.
  e.g.

  • localhost:8080/prometheus
  • localhost:8090/prometheus
  • localhost:8070/prometheus

• How to use: https://docs.spring.io/spring-boot/docs/current/reference/htmlsingle/#production-ready-metrics-export-prometheus

[codecov-io]

Codecov Report

Merging #2507 into master will increase coverage by 8.32%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master    #2507      +/-   ##
============================================
+ Coverage     50.19%   58.51%   +8.32%     
+ Complexity     2046     1174     -872     
============================================
  Files           410      196     -214     
  Lines         12555     5942    -6613     
  Branches       1285      636     -649     
============================================
- Hits           6302     3477    -2825     
+ Misses         5806     2204    -3602     
+ Partials        447      261     -186

Impacted Files	Coverage Δ	Complexity Δ
...amework/apollo/common/controller/WebMvcConfig.java	0% <ø> (ø)	0 <0> (ø)	⬇️
.../portal/spi/configuration/LdapGroupProperties.java
...ework/apollo/portal/controller/ItemController.java
...o/configservice/wrapper/DeferredResultWrapper.java
...omponent/emailbuilder/GrayPublishEmailBuilder.java
...k/apollo/portal/controller/FavoriteController.java
...apollo/portal/entity/vo/AppRolesAssignedUsers.java
...nfigservice/ConfigServerEurekaServerConfigure.java
...ponent/emailbuilder/NormalPublishEmailBuilder.java
.../framework/apollo/portal/entity/vo/SystemInfo.java
... and 204 more

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[coveralls]

Coverage increased (+0.004%) to 53.76% when pulling d2afe49 on prometheus into fd231ab on master.

[nobodyiam]

LGTM