qmldom: add Minimal DomCreationOption for QDS

DOM construction time is quite slow for the QDS use case, so add a new
minimal DomCreationOptions that ignores comments (as QDS has no need
for comments) because comments seem to take some time to construct.

Add the Minimal DomCreationOptions to the Benchmark to show that it is
faster then using the Default DomCreationOptions.

Measured on my machine, using a release build:
File                | Default (ms) | Minimal (ms) | Speedup
tiger.qml           | 83           | 38           | 2.18
deeplyNested.qml    | 438          | 12           | 36.5

The 36.5 speedup does look weird at first, but a quick look in the
profiler shows that we spend 95% of the benchmark time for
deeplyNested.qml with Default DomCreationOptions in
* Path::component() and
* DomItem::field()
while trying to iterate on the Qml Document to find the comments.

So its not a bug, its just the linear complexity of Path::component()
and DomItem::field() that proves to be inadequate in our case:
* Path::component(i) returns the i.th path component, and needs to
  iterate through all components to find it
* DomItem::field(f) returns the value of the field f, and uses
  iterateDirectSubpaths() which is linear in the number of total fields,
  and it seems the laziness there might not be working as expected.

Pick-to: 6.8 6.9
Task-number: QTBUG-92889
Change-Id: I51168b68e930ed14d1751cf0f6028b1b2879b774
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
Reviewed-by: Olivier De Cannière <olivier.decanniere@qt.io>

src/qmldom/qqmldomconstants_p.h

@@ -414,6 +414,7 @@ Q_ENUM_NS(FileLocationRegion);
 enum DomCreationOption : char {
     Default, // required by qmlformat for example
     Extended, // required by qmlls for example
+    Minimal, // required by QmlDocumentParser in Qt Design Studio, for example
 };
 
 } // end namespace Dom

src/qmldom/qqmldomtop.cpp

@@ -2241,6 +2241,10 @@ void DomEnvironment::populateFromQmlFile(MutableDomItem &&qmlFile)
             Q_UNUSED(this); // note: integrity requires "this" to be in the capture list, while
                             // other compilers complain about "this" being unused in the lambda
             AST::Node::accept(qmlFilePtr->ast(), visitor);
+
+            if (m_domCreationOption == DomCreationOption::Minimal)
+                return;
+
             CommentCollector collector(qmlFile);
             collector.collectComments();
         };

tests/benchmarks/qml/qmldom/tst_qmldomconstruction.cpp

@@ -32,6 +32,9 @@ void tst_qmldomconstruction::domConstructionTime_data()
 
     QTest::addRow("extended-tiger.qml") << baseDir + u"/longQmlFile.qml"_s << Extended;
     QTest::addRow("extended-deeplyNested.qml") << baseDir + u"/deeplyNested.qml"_s << Extended;
+
+    QTest::addRow("minimal-tiger.qml") << baseDir + u"/longQmlFile.qml"_s << Minimal;
+    QTest::addRow("minimal-deeplyNested.qml") << baseDir + u"/deeplyNested.qml"_s << Minimal;
 }
 
 void tst_qmldomconstruction::domConstructionTime()