[#796][0.7] bug: Fix the issues of MetricReporter

[xianjingfeng]

What changes were proposed in this pull request?

1. Support custom config keys defined in plugins
2. Refactor the logic for load config file
3. Fix some issues of metricReporter.

Why are the changes needed?

Metric reporter is unusable.
Fix: #796

Does this PR introduce any user-facing change?

No.

How was this patch tested?

UT and Manual testing

[codecov-commenter]

Codecov Report

Merging #821 (20a0a9a) into branch-0.7 (6857ea5) will decrease coverage by 0.12%.
The diff coverage is 13.04%.

@@               Coverage Diff                @@
##             branch-0.7     #821      +/-   ##
================================================
- Coverage         60.89%   60.78%   -0.12%     
+ Complexity         1800     1792       -8     
================================================
  Files               214      214              
  Lines             12386    12374      -12     
  Branches           1042     1045       +3     
================================================
- Hits               7543     7521      -22     
- Misses             4440     4449       +9     
- Partials            403      404       +1     

Impacted Files	Coverage Δ
.../org/apache/uniffle/common/config/RssBaseConf.java	96.34% <0.00%> (+2.29%)	⬆️
...java/org/apache/uniffle/common/config/RssConf.java	29.93% <0.00%> (-2.48%)	⬇️
...rometheus/PrometheusPushGatewayMetricReporter.java	74.46% <0.00%> (ø)
.../apache/uniffle/coordinator/CoordinatorServer.java	56.45% <0.00%> (-0.93%)	⬇️
.../java/org/apache/uniffle/server/ShuffleServer.java	63.51% <0.00%> (-0.88%)	⬇️
.../uniffle/common/metrics/MetricReporterFactory.java	57.14% <100.00%> (ø)
...rg/apache/uniffle/coordinator/CoordinatorConf.java	98.70% <100.00%> (+1.11%)	⬆️
...a/org/apache/uniffle/server/ShuffleServerConf.java	99.28% <100.00%> (-0.04%)	⬇️

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[xianjingfeng]

It seems that this PR is merged to master in CI enviroment. But the first time is ok.
https://github.com/apache/incubator-uniffle/actions/runs/4684746312/jobs/8301194063

Do you know why? @kaijchen @jerqi

[jerqi]

It seems that this PR is merged to master in CI enviroment. But the first time is ok. https://github.com/apache/incubator-uniffle/actions/runs/4684746312/jobs/8301194063

Do you know why? @kaijchen @jerqi

I cherry-pick a wrong commit. I have reverted it. it's strange that it influence your pr. You could rerun your pr.

[kaijchen]

You could rerun your pr.

Please rebase or merge branch-0.7.

[jerqi]

You could rerun your pr.

Please rebase or merge branch-0.7.

But his commit history don't have my mistake commit. It's strange. But the error seems that it caused by my mistake commit.

[xianjingfeng]

It is ok now, just reopen it.

[jerqi]

LGTM, thanks @xianjingfeng