convertWellSchema.py silently drops every XML comment

Description

scripts/convertWellSchema.py removes every comment from the deck it converts. The loss is silent: the script reports XSD validation passed and the output is valid, so nothing signals that anything was lost.

GEOS decks use comments to record why a value was chosen — a solver tolerance, a rate derivation, the identity of a saturation table. None of that is recoverable from the output.

Root cause

The script reads the deck with xml.etree.ElementTree, which discards comments by default. Three call sites are affected:

• update_constraint_element() — line 100
• removeUseMass() — line 301
• add_we() — line 323

All three call tree = ET.parse(xml_file).

A second, separate loss affects the prolog. xml.etree keeps no node before the root element, so a header comment before <Problem> is dropped even after the parser is fixed.

Steps to reproduce

1. Take any deck with <WellControls> and at least one comment.
2. Run python3 scripts/convertWellSchema.py -s deck.xml -t out.xml --xsd src/coreComponents/schema/schema.xsd.
3. Compare grep -c '<!--' deck.xml with grep -c '<!--' out.xml.

Observed on two decks: 3 comments to 0, and 5 comments to 0.

Suggested fix

1. Pass a comment-preserving parser at the three call sites: ET.XMLParser(target=ET.TreeBuilder(insert_comments=True)).
2. Read the prolog comments with lxml before the conversion writes anything, then put them back afterwards. The read must come first, because --replace is the default and the source and the target are then the same file.

A PR follows.

Environment

GEOS develop at 24a8410b51, Python 3.11, lxml 6.1.2.

Start in scripts/convertWellSchema.py at update_constraint_element(), removeUseMass(), and add_we(), then reproduce the loss with the supplied command and comment counts. Review how the three ET.parse call sites handle comments and how the prolog is read before --replace writes the target. Done means inline and pre-root comments survive conversion and validation still passes.