LaTeX backend strips the first-line indentation of verbatim and lstlisting code #4501

Bug

Same problem as #4485 (fixed for Markdown in #4487), in the LaTeX backend. _extract_verbatim_content (docling/backend/latex/utils/text.py) returns match.group(1).strip(), which removes the leading indentation of the first code line while later lines keep theirs. The relative indentation changes, so the code itself is altered.

It affects verbatim and lstlisting (both go through this function). Code whose first line is not indented is unaffected.

Steps to reproduce

from io import BytesIO

from docling.datamodel.base_models import DocumentStream, InputFormat
from docling.document_converter import DocumentConverter

tex = (
    "\\documentclass{article}\n\\begin{document}\n"
    "\\begin{verbatim}\n  key: 1\n  sub:\n    x: 2\n\\end{verbatim}\n"
    "\\end{document}\n"
)
doc = DocumentConverter(allowed_formats=[InputFormat.LATEX]).convert(
    DocumentStream(name="a.tex", stream=BytesIO(tex.encode()))
).document
print([t.text for t in doc.texts if t.label == "code"])

Actual: ['key: 1\n sub:\n x: 2']
Expected: [' key: 1\n sub:\n x: 2']

Docling version

2.132.0 (main @ a1c5ff2)

Python version

3.12.14

I'd like to send a PR, using the same trimming as #4487.