Resolves: tdf#133812 Add the 'Result' style again used by the Subtotal tool

Necessary to also adapt the test case that checks for a defined
number of styles.

Regression from

    commit 7b0aed617f
    CommitDate: Wed Sep 28 11:42:56 2016 +0000

        Remove old cell styles from calc

and

    commit 06f3199371
    CommitDate: Sun Oct 2 13:51:26 2016 +0000

        tdf#90937 Add a set of cell styles to calc

Change-Id: I3e47d8e24d375a64d9056e7a85197b89173c8e41
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/103520
Tested-by: Jenkins
Reviewed-by: Eike Rathke <erack@redhat.com>

sc/qa/extras/scstylefamilyobj.cxx

@@ -83,10 +83,14 @@ private:
     uno::Reference<lang::XComponent> m_xComponent;
 };
 
+/* TODO: this c/should be derived/defined from the real style count, default
+ * implemented plus sc/res/xml/styles.xml */
+constexpr sal_Int32 kScStyleFamilyObjCount = 20;
+
 ScStyleFamilyObj::ScStyleFamilyObj()
     : CalcUnoApiTest("/sc/qa/extras/testdocuments")
     , XElementAccess(cppu::UnoType<style::XStyle>::get())
-    , XIndexAccess(19)
+    , XIndexAccess(kScStyleFamilyObjCount)
     , XNameAccess("ScStyleFamilyObj")
     , XNameContainer("ScStyleFamilyObj")
     , XNameReplace("ScStyleFamilyObj")

sc/res/xml/styles.xml

@@ -57,4 +57,8 @@
     <style:style style:name="Accent 3" style:family="table-cell" style:parent-style-name="Accent">
         <style:table-cell-properties fo:background-color="#dddddd"/>
     </style:style>
+
+    <style:style style:name="Result" style:family="table-cell" style:parent-style-name="Default">
+        <style:text-properties fo:font-weight="bold" fo:font-style="italic" style:text-underline-style="solid"/>
+    </style:style>
 </office:styles>