Investigate whether D2 map import should preserve the requested tileset/rules

[evgeniysergeev]

D2MapImporter.Import(filename, mod, tileset, rules) still accepts tileset and rules, but the importer currently initializes terrain using the hardcoded "arrakis2" tileset and does not use the passed Ruleset.
Investigate whether this is intentional or whether the importer should propagate the requested tileset/rules into map initialization. If needed, update D2MapImporter so imported maps are created with the caller-provided tileset/rules instead of relying on hardcoded defaults.
Points to check:

• Whether all current D2 imports are expected to use only "arrakis2".
• Whether D2ImportMapD2Command passing args[2] should affect the imported map.
• Whether Ruleset.LoadDefaultsForTileSet(...) is expected to be reflected in the resulting Map.
• Whether keeping unused tileset / rules parameters is still useful or should be cleaned up.