tdf#129525 writerfilter: ignore GOTOBUTTON field

The bugdoc contains nested fields for some of the page numbers:

{\field\flddirty{\*\fldinst {\caps0\lang1024  GOTOBUTTON _Toc434317064  }{\field{\*\fldinst {\caps0\lang1024  PAGEREF _Toc434317064 }}{\fldrslt {\caps0\lang1024 4}}}}}

The problem is that the outer field does not have a \fldrslt, only the
inner PAGEREF field has one.

This used to be imported incorrectly because the nested field's result
ended up in the outer field's result; now it's imported correctly but
then there's no field result to show, because Writer can't expand
fieldmarks.

As we can't do anything with a GOTOBUTTON field, just ignore it
explicitly to prevent creating a generic fieldmark; the PAGEREF is
already ignored inside of a ToX since commit
9679e9c23216decb5f9f25f85b04cb3f25211111.

("regression" from e511a0ca5dde6d731bb126bbfe21768867890102..d9030ad6298e2f49ee63489d6158ea6ad23c0111)

Change-Id: I8135c8d14995378181ce959d22d9be5ea0cae260
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/86796
Tested-by: Jenkins
Reviewed-by: Michael Stahl <michael.stahl@cib.de>
diff --git a/writerfilter/source/dmapper/DomainMapper_Impl.cxx b/writerfilter/source/dmapper/DomainMapper_Impl.cxx
index 75b6133..eaa720d 100644
--- a/writerfilter/source/dmapper/DomainMapper_Impl.cxx
+++ b/writerfilter/source/dmapper/DomainMapper_Impl.cxx
@@ -3713,7 +3713,7 @@
        {"FORMCHECKBOX",    {"",                        FIELD_FORMCHECKBOX  }},
        {"FORMDROPDOWN",    {"DropDown",                FIELD_FORMDROPDOWN  }},
        {"FORMTEXT",        {"Input",                   FIELD_FORMTEXT      }},
//      {"GOTOBUTTON",      {"",                        FIELD_GOTOBUTTON    }},
        {"GOTOBUTTON",      {"",                        FIELD_GOTOBUTTON    }},
        {"HYPERLINK",       {"",                        FIELD_HYPERLINK     }},
        {"IF",              {"ConditionalText",         FIELD_IF            }},
//      {"INFO",            {"",                        FIELD_INFO          }},
@@ -4677,6 +4677,7 @@
                case FIELD_EQ:
                case FIELD_INCLUDEPICTURE:
                case FIELD_SYMBOL:
                case FIELD_GOTOBUTTON:
                        bCreateField = false;
                        break;
                case FIELD_FORMCHECKBOX :