[clang-doc] enable comments in class templates (#149848)

The Mustache basic project has comments in its headers but the comments were not
serialized. Now we serialize \brief and paragraph comments for classes
and add that output to the basic project test.

Author: evelez7

clang-tools-extra/clang-doc/assets/class-template.mustache

@@ -128,11 +128,11 @@
             <section class="hero section-container">
                 <div class="hero__title">
                     <h1 class="hero__title-large">{{TagType}} {{Name}}</h1>
-                    {{#RecordComments}}
+                    {{#Description}}
                     <div class="hero__subtitle">
                         {{>Comments}}
                     </div>
-                    {{/RecordComments}}
+                    {{/Description}}
                 </div>
             </section>
             {{#HasPublicMembers}}

clang-tools-extra/clang-doc/assets/comment-template.mustache

@@ -5,11 +5,16 @@
     
     This file defines templates for generating comments
 }}
-{{#FullComment}}
+{{#BriefComments}}
     {{#Children}}
     {{>Comments}}
     {{/Children}}
-{{/FullComment}}
+{{/BriefComments}}
+{{#ParagraphComments}}
+    {{#Children}}
+    {{>Comments}}
+    {{/Children}}
+{{/ParagraphComments}}
 {{#ParagraphComment}}
     {{#Children}}
     {{>Comments}}

clang-tools-extra/test/clang-doc/basic-project.mustache.test

@@ -60,6 +60,17 @@ HTML-SHAPE:         <div class="content">
 HTML-SHAPE:             <section class="hero section-container">
 HTML-SHAPE:                 <div class="hero__title">
 HTML-SHAPE:                     <h1 class="hero__title-large">class Shape</h1>
+HTML-SHAPE:                    <div class="hero__subtitle">
+HTML-SHAPE:                                    <div>
+HTML-SHAPE:                                        <p> Abstract base class for shapes.</p>
+HTML-SHAPE:                                    </div>
+HTML-SHAPE:                                        <div>
+HTML-SHAPE:                                    <p></p>
+HTML-SHAPE:                                </div>
+HTML-SHAPE:                                    <div>
+HTML-SHAPE:                                    <p> Provides a common interface for different types of shapes.</p>
+HTML-SHAPE:                                </div>
+HTML-SHAPE:                                                </div>
 HTML-SHAPE:                 </div>
 HTML-SHAPE:             </section>
 HTML-SHAPE:             <section id="PublicMethods" class="section-container">
@@ -172,6 +183,16 @@ HTML-CALC:         <div class="content">
 HTML-CALC:             <section class="hero section-container">
 HTML-CALC:                 <div class="hero__title">
 HTML-CALC:                     <h1 class="hero__title-large">class Calculator</h1>
+HTML-CALC:                                    <div>
+HTML-CALC:                                        <p> A simple calculator class.</p>
+HTML-CALC:                                    </div>
+HTML-CALC:                                        <div>
+HTML-CALC:                                    <p></p>
+HTML-CALC:                                </div>
+HTML-CALC:                                    <div>
+HTML-CALC:                                    <p> Provides basic arithmetic operations.</p>
+HTML-CALC:                                </div>
+HTML-CALC:                                                </div>
 HTML-CALC:                 </div>
 HTML-CALC:             </section>
 HTML-CALC:             <section id="PublicMembers" class="section-container">
@@ -300,6 +321,17 @@ HTML-RECTANGLE:         <div class="content">
 HTML-RECTANGLE:             <section class="hero section-container">
 HTML-RECTANGLE:                 <div class="hero__title">
 HTML-RECTANGLE:                     <h1 class="hero__title-large">class Rectangle</h1>
+HTML-RECTANGLE:                    <div class="hero__subtitle">
+HTML-RECTANGLE:                                    <div>
+HTML-RECTANGLE:                                        <p> Rectangle class derived from Shape.</p>
+HTML-RECTANGLE:                                    </div>
+HTML-RECTANGLE:                                        <div>
+HTML-RECTANGLE:                                    <p></p>
+HTML-RECTANGLE:                                </div>
+HTML-RECTANGLE:                                    <div>
+HTML-RECTANGLE:                                    <p> Represents a rectangle with a given width and height.</p>
+HTML-RECTANGLE:                                </div>
+HTML-RECTANGLE:                                                </div>
 HTML-RECTANGLE:                 </div>
 HTML-RECTANGLE:             </section>
 HTML-RECTANGLE:             <section id="PublicMethods" class="section-container">
@@ -395,6 +427,17 @@ HTML-CIRCLE:         <div class="content">
 HTML-CIRCLE:             <section class="hero section-container">
 HTML-CIRCLE:                 <div class="hero__title">
 HTML-CIRCLE:                     <h1 class="hero__title-large">class Circle</h1>
+HTML-CIRCLE:                    <div class="hero__subtitle">
+HTML-CIRCLE:                                    <div>
+HTML-CIRCLE:                                        <p> Circle class derived from Shape.</p>
+HTML-CIRCLE:                                    </div>
+HTML-CIRCLE:                                        <div>
+HTML-CIRCLE:                                    <p></p>
+HTML-CIRCLE:                                </div>
+HTML-CIRCLE:                                    <div>
+HTML-CIRCLE:                                    <p> Represents a circle with a given radius.</p>
+HTML-CIRCLE:                                </div>
+HTML-CIRCLE:                                                </div>
 HTML-CIRCLE:                 </div>
 HTML-CIRCLE:             </section>
 HTML-CIRCLE:             <section id="PublicMethods" class="section-container">