Support restoreXmlTree for funcdata

[5c4lar]

Is your feature request related to a problem? Please describe.
I'm trying to decompile the whole program and do some analysis with the lifted. For large programs, it's time-consuming to do the decompilation every time, I wish to save the Funcdata as XML and load it back to restore the decompilation result.

Describe the solution you'd like
restoreXmlTree method implemented for Funcdata and some options to support this when calling Architecture.saveXml.

Additional context

/// A single \<ast> tag is produced with children describing Varnodes, PcodeOps, and
/// basic blocks making up \b this function's current syntax tree.
/// \param s is the output stream
void Funcdata::saveXmlTree(ostream &s) const

{
  s << "<ast>\n";
  s << "<varnodes>\n";
  for(int4 i=0;i<glb->numSpaces();++i) {
    AddrSpace *base = glb->getSpace(i);
    if (base == (AddrSpace *)0 || base->getType()==IPTR_IOP) continue;
    VarnodeLocSet::const_iterator iter = vbank.beginLoc(base);
    VarnodeLocSet::const_iterator enditer = vbank.endLoc(base);
    saveVarnodeXml(s,iter,enditer);
  }
  s << "</varnodes>\n";
  
  list<PcodeOp *>::iterator oiter,endoiter;
  PcodeOp *op;
  BlockBasic *bs;
  for(int4 i=0;i<bblocks.getSize();++i) {
    bs = (BlockBasic *)bblocks.getBlock(i);
    s << "<block";
    a_v_i(s,"index",bs->getIndex());
    s << ">\n";
    bs->saveXmlBody(s);
    oiter = bs->beginOp();
    endoiter = bs->endOp();
    while(oiter != endoiter) {
      op = *oiter++;
      op->saveXml(s);
      s << '\n';
    }
    s << "</block>\n";
  }
  for(int4 i=0;i<bblocks.getSize();++i) {
    bs = (BlockBasic *)bblocks.getBlock(i);
    if (bs->sizeIn() == 0) continue;
    s << "<blockedge";
    a_v_i(s,"index",bs->getIndex());
    s << ">\n";
    bs->saveXmlEdges(s);
    s << "</blockedge>\n";
  }
  s << "</ast>\n";
}

saveXml is here, but I cannot find a proper way to call this. Nor can I find the right API to restore the XmlTree from the dumped ast.