fix(createSSURGO) connection names, file matching, and append/overwrite table logic

[AndrewBrown-USDA]

Refines createSSURGO() to improve database connection handling, output reporting, file matching, and append/overwrite argument logic for writing tables.

• Now extracts the database name from any DBIConnection object using DBI::dbGetInfo(conn)$dbname
  • Output reporting is simplified to always use the resolved filename variable, rather than conditionally accessing conn@dbname, which may not exist depending on driver/connection type (note: it was removed in recent versions of {duckdb})
• The logic for matching spatial files (f.shp.sc) is now more efficient by generating filename prefixes and matching them against the base names of files
• The append and overwrite arguments for writing tables is clarified: append=TRUE takes precedence, overwrite=TRUE is handled explicitly; otherwise, default values are set.