Two V3000 export issues: implict H cause wrong index on s groups, and reversed order for COLLECTON / SGroup Blocks.

**Summary**
Inside molfile_saver.cpp, function: void MolfileSaver::_writeCtab(Output& output, BaseMolecule& mol, bool query):

1. Issue in V3000 implicit h toggle causing the the S group total count referenced in memory to be modified, causing a failure in parsing the S group when reading from RDKit as it thinks the file is corrupted.

2. Issue in V3000 export of M V30 BEGIN COLLECTION block occuring before M V30 BEGIN SGROUP block, causing RDKit failing to parse the section.

**Steps to Reproduce**
Import the RxN . Export and import to RDKit. See Failures. The test file had been provided under attachment section.

**Expected behavior/Actual Behavior**
### Issue 1
First on the issue of improper S group counting:
```
else if (add_implicit_h && Molecule::shouldWriteHCount(mol.asMolecule(), i) && hcount > 0)
{
int sg_idx;

sg_idx = mol.sgroups.addSGroup(SGroup::SG_TYPE_DAT);
DataSGroup& sgroup = (DataSGroup&)mol.sgroups.getSGroup(sg_idx);

sgroup.atoms.push(i);

QS_DEF(Array, tmp_buf);
ArrayOutput tmp_out(tmp_buf);
tmp_out.printf("IMPL_H%d", hcount);
tmp_buf.push(0);
sgroup.data.readString(tmp_buf.ptr(), true);

sgroup.name.readString("MRV_IMPLICIT_H", true);
sgroup.detached = true;
}
```
The section of the code above adds new s groups to mol.sgroups object while the execution is still in progress exporting the data, and more importantly, this was added **AFTER** the following line was already exported to the text file I/O:

```
output.writeStringCR("M V30 BEGIN CTAB");
output.printfCR("M V30 COUNTS %d %d %d 0 0", mol.vertexCount(), mol.edgeCount(), mol.countSGroups());
output.writeStringCR("M V30 BEGIN ATOM");
```

So, when implicit H is added, total S group counter written already in an earlier line had become incorrect.

### Issue 2

Per this technical manual:
https://www.daylight.com/meetings/mug05/Kappler/ctfile.pdf
In page 85 to page 90, the order of BEGIN SGROPU and BEGIN COLLECTION is defined. RDKit follows this strict ordering while Indigo writes it in reverse. It causes toolkit compatibility issue when read by another tool.

The following block of code:
```
MoleculeStereocenters& stereocenters = mol.stereocenters;

if (stereocenters.begin() != stereocenters.end() || mol.hasHighlighting())
{
output.writeStringCR("M V30 BEGIN COLLECTION");

QS_DEF(Array, processed);

processed.clear_resize(mol.vertexEnd());
processed.zerofill();

for (i = mol.vertexBegin(); i != mol.vertexEnd(); i = mol.vertexNext(i))
{
if (processed[i])
continue;

ArrayOutput out(buf);
int j, type = stereocenters.getType(i);

if (type == MoleculeStereocenters::ATOM_ABS)
out.writeString("MDLV30/STEABS ATOMS=(");
else if (type == MoleculeStereocenters::ATOM_OR)
out.printf("MDLV30/STEREL%d ATOMS=(", stereocenters.getGroup(i));
else if (type == MoleculeStereocenters::ATOM_AND)
out.printf("MDLV30/STERAC%d ATOMS=(", stereocenters.getGroup(i));
else
continue;

QS_DEF(Array, list);

list.clear();
list.push(i);

for (j = mol.vertexNext(i); j < mol.vertexEnd(); j = mol.vertexNext(j))
if (stereocenters.sameGroup(i, j))
{
list.push(j);
processed[j] = 1;
}

out.printf("%d", list.size());
for (j = 0; j < list.size(); j++)
out.printf(" %d", _atom_mapping[list[j]]);
out.writeChar(')');

_writeMultiString(output, buf.ptr(), buf.size());
}

if (mol.hasHighlighting())
{
if (mol.countHighlightedBonds() > 0)
{
ArrayOutput out(buf);

out.printf("MDLV30/HILITE BONDS=(%d", mol.countHighlightedBonds());

for (i = mol.edgeBegin(); i != mol.edgeEnd(); i = mol.edgeNext(i))
if (mol.isBondHighlighted(i))
out.printf(" %d", _bond_mapping[i]);
out.writeChar(')');

_writeMultiString(output, buf.ptr(), buf.size());
}
if (mol.countHighlightedAtoms() > 0)
{
ArrayOutput out(buf);
out.printf("MDLV30/HILITE ATOMS=(%d", mol.countHighlightedAtoms());
for (i = mol.vertexBegin(); i != mol.vertexEnd(); i = mol.vertexNext(i))
if (mol.isAtomHighlighted(i))
out.printf(" %d", _atom_mapping[i]);
out.writeChar(')');

_writeMultiString(output, buf.ptr(), buf.size());
}
}
if (mol.custom_collections.size() > 0)
{
for (i = mol.custom_collections.begin(); i != mol.custom_collections.end(); i = mol.custom_collections.next(i))
{
ArrayOutput out(buf);
out.printf("%s", mol.custom_collections.at(i));
_writeMultiString(output, buf.ptr(), buf.size());
}
}

output.writeStringCR("M V30 END COLLECTION");
}
```
I think, should be moved to right AFTER
```
output.writeStringCR("M V30 END SGROUP");
}
```

**Attachments**
[stereo_reaction.zip](https://github.com/user-attachments/files/16149365/stereo_reaction.zip)

If applicable, add attachment files to reproduce the issue.

**Additional context**
Add any other context about the problem here.