Fix formula text truncated on XML character references

[sentinelt]

Summary

dataValidation / formula character data that contains XML numeric character references (e.g. – for an en-dash) was truncated when reading .xlsx files.

Root cause

quick-xml emits those references as Event::GeneralRef nodes between successive Event::Text fragments. The parsers for DataValidation (formula1 / formula2) and Formula replaced the accumulator on each Text event and ignored GeneralRef, so only the last text fragment survived.

Example list formula in a real workbook:

<formula1>"0&#8211;3 years ago,4&#8211;5 years ago,6&#8211;7 years ago"</formula1>

was read as:

7 years ago"

instead of the full list string.

Fix

• Append successive Text events instead of overwriting
• Resolve and append GeneralRef (numeric char refs + common named entities)
• Shared helpers: append_xml_text / append_xml_general_ref
• Unit tests covering en-dash list formulas and plain list formulas
• Close a missing brace in number_formater tests that broke compilation of the local tree

[MathNya]

@sentinelt
Thank you for the PR.
Since there were no issues with the changes, I’ll go ahead and merge them.
(I’ll make a few minor adjustments after merging.)

There are a few other instances of this, so it looks like we’ll need to review the entire code.

[c-git]

@MathNya after you've done the update in the other places as well, please let me know so I can test if it also fixes my issue in #336

[MathNya]

@c-git
We have addressed all the issues.
Please check #336.