read_tpc is a fine function but usually we just send the data bytes even though the filepath is sometimes available. This pr modifies read_tpc so it'll attempt to look for the txi.
if source is a filepath to a tpc/tga, attempt to see if the txi is in the same dir with CaseAwarePath
if txi_source provided, override whatever was in the txi with that data and return it.
read_tpcis a fine function but usually we just send the data bytes even though the filepath is sometimes available. This pr modifiesread_tpcso it'll attempt to look for the txi.