refactor: conditionally render comment for theme

[guqing]

What type of PR is this?

/kind improvement
/area core
/milestone 2.8.x
/area theme

What this PR does / why we need it:

按条件渲染评论组件以简化主题端对评论组件是否显示的条件控制

使用了评论标签的模板页面都能直接使用 ${haloCommentEnabled} 取值能得到评论组件是否可见的结果为true/false 用于在需要级联条件渲染的组件上使用，如：

<!-- 评论组件不可见时不渲染标题 -->
<p th:if="${haloCommentEnabled}">评论</p>
<halo:comment />

how to test it?
在主题端未加渲染条件时：

1. 测试全局评论组件是否开启的设置是否有效
2. 测试文章和自定义页面是否开启评论的设置是否有效
3. 测试评论组件启用和停止时评论组件的渲染是否正确
4. 测试 ${haloCommentEnabled} 结果是否正确

Which issue(s) this PR fixes:

Fixes #4137

Does this PR introduce a user-facing change?

按条件渲染评论组件以简化主题端对评论组件是否显示的条件控制

[codecov]

Codecov Report

Merging #4271 (ca1f12a) into main (15dd782) will decrease coverage by 0.09%.
The diff coverage is 100.00%.

@@             Coverage Diff              @@
##               main    #4271      +/-   ##
============================================
- Coverage     60.71%   60.62%   -0.09%     
- Complexity     2489     2498       +9     
============================================
  Files           369      370       +1     
  Lines         12994    13047      +53     
  Branches        933      935       +2     
============================================
+ Hits           7889     7910      +21     
- Misses         4645     4678      +33     
+ Partials        460      459       -1     

Impacted Files	Coverage Δ
.../app/theme/dialect/CommentElementTagProcessor.java	100.00% <100.00%> (ø)
.../java/run/halo/app/theme/router/ModelMapUtils.java	94.73% <100.00%> (+0.61%)	⬆️

... and 9 files with indirect coverage changes

[LIlGG]

/lgtm

[guqing]

Note: 此 PR 合并后需要添加主题使用评论的文档

[ruibaby]

/approve

[f2c-ci-robot]

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