Refine problem detail when plugin is already installed

[JohnNiang]

What type of PR is this?

/kind improvement
/area core

What this PR does / why we need it:

This PR refines problem detail of PluginAlreadyExistsException. Please note the new type https://halo.run/probs/plugin-alreay-exists and additional property pluginName of problem detail.

Meanwhile

• Before

  {
    "type": "about:blank",
    "title": "Plugin Already Exists Error",
    "status": 400,
    "detail": "Plugin PluginCommentWidget already exists.",
    "instance": "/apis/api.console.halo.run/v1alpha1/plugins/install",
    "requestId": "880fe8cd-5",
    "timestamp": "2023-02-20T10:17:21.541104Z"
  }

• After

  {
    "type": "https://halo.run/probs/plugin-alreay-exists",
    "title": "Plugin Already Exists Error",
    "status": 400,
    "detail": "Plugin PluginCommentWidget already exists.",
    "instance": "/apis/api.console.halo.run/v1alpha1/plugins/install",
    "pluginName": "PluginCommentWidget",
    "requestId": "880fe8cd-5",
    "timestamp": "2023-02-20T10:17:21.541104Z"
  }

Which issue(s) this PR fixes:

Fixes #3164

Special notes for your reviewer:

Does this PR introduce a user-facing change?

优化插件重复安装错误提示。

[ruibaby]

/approve

[f2c-ci-robot]

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This pull-request has been approved by: ruibaby

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[guqing]

/lgtm