tdf#147742 a11y: AccessibleGridControlBase: get accessible desc on demand

Previously, the accessible description was retrieved
in the `AccessibleGridControlBase` ctor and stored
in a class member. Change that to fetch the
description on demand.

`TableControl::GetAccessibleObjectDescription` is used
to get the description, which currently uses the row and
column index of the currently active cell.

When using the macro from the sample document in tdf#147742
with the Orca screen reader active, no cell was active
at the point that the ctor was called, so
`ROW_INVALID`/`COL_INVALID` were used, resulting
in a crash later (s. backtrace in tdf#147742).

If necessary, `TableControl::GetAccessibleObjectDescription`
could be extended to allow passing an explicit row/column index,
as is the case for `TableControl::GetAccessibleName`, then
override `AccessibleGridControlBase::getAccessibleDescription`
in `AccessibleGridControlCell`, similar to how it is done
for the accessible name in
Change-Id I87eabb2ce3c99d4a622d919ab0fb8d7fb3beed6b
("tdf#147742 a11y: AccessibleGridControl...: get accessible name on
demand").

Change-Id: I58f3a2b0c83e2cdbae103811505d7d0a4f8bfc52
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/130934
Tested-by: Jenkins
Reviewed-by: Michael Weghorn <m.weghorn@posteo.de>
diff --git a/accessibility/inc/extended/AccessibleGridControlBase.hxx b/accessibility/inc/extended/AccessibleGridControlBase.hxx
index 4075b7f..7da777d8 100644
--- a/accessibility/inc/extended/AccessibleGridControlBase.hxx
+++ b/accessibility/inc/extended/AccessibleGridControlBase.hxx
@@ -253,8 +253,6 @@ protected:
    ::vcl::table::AccessibleTableControlObjType m_eObjType;

private:
    /** Localized description text. */
    OUString m_aDescription;
    ::comphelper::AccessibleEventNotifier::TClientId    m_aClientId;
};

diff --git a/accessibility/source/extended/AccessibleGridControlBase.cxx b/accessibility/source/extended/AccessibleGridControlBase.cxx
index c02d921..915aeb7 100644
--- a/accessibility/source/extended/AccessibleGridControlBase.cxx
+++ b/accessibility/source/extended/AccessibleGridControlBase.cxx
@@ -54,7 +54,6 @@ AccessibleGridControlBase::AccessibleGridControlBase(
    m_xParent( rxParent ),
    m_aTable( rTable),
    m_eObjType( eObjType ),
    m_aDescription( rTable.GetAccessibleObjectDescription( eObjType ) ),
    m_aClientId(0)
{
}
@@ -134,7 +133,7 @@ OUString SAL_CALL AccessibleGridControlBase::getAccessibleDescription()
    SolarMutexGuard g;

    ensureIsAlive();
    return m_aDescription;
    return m_aTable.GetAccessibleObjectDescription(m_eObjType);
}

OUString SAL_CALL AccessibleGridControlBase::getAccessibleName()