SLUDGE: NSC Crashes in opening credits

[henke37]

The game attempts to loadCustomData from the game data folder instead of the save folder.

[henke37]

Partial fix, now fails encoding check

[Azzurra Suffia <azzurra.suffia@…>]

In 7bdaa656:

SLUDGE: Fix data file encoding and restore CP1252 compatibility

The SLUDGE engine originally used CP1252 encoding for its data file
validation strings. During code conversion, this string was
accidentally transcoded to UTF-8 in the source code, causing ScummVM
to write headers that deviated from the original engine's format.

This change:

• Restores the original CP1252 validation string for all new writes.

• Implements a fallback to accept the UTF-8 validation string for backward compatibility with files created by previous ScummVM builds.

• Ensures consistency with the original SLUDGE data format.

Fix #13711

[sev-]

Fixed