Support obtaining plugins root in plugins

[JohnNiang]

What type of PR is this?

/kind feature
/kind api-change
/area core
/area plugin

What this PR does / why we need it:

This PR supports obtaining plugins root in plugins. Below is an example in plugin:

@Component
class PluginsRootGetterDemo {

    private final PluginsRootGetter pluginsRootGetter;

    PluginsRootGetterDemo(PluginsRootGetter pluginsRootGetter) {
        this.pluginsRootGetter = pluginsRootGetter;
    }

}

Meanwhile, I remove the PluginProperties#pluginsRoot for a clear way to obtain plugins root.

Does this PR introduce a user-facing change?

支持在插件中获取插件根目录

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 58.26%. Comparing base (bc10336) to head (57a63e1).
Report is 62 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #6269      +/-   ##
============================================
+ Coverage     54.51%   58.26%   +3.75%     
- Complexity     3523     3759     +236     
============================================
  Files           646      647       +1     
  Lines         21862    21950      +88     
  Branches       1528     1541      +13     
============================================
+ Hits          11917    12790     +873     
+ Misses         9328     8542     -786     
- Partials        617      618       +1     

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[ruibaby]

/lgtm

[f2c-ci-robot]

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