Move Rinex features from gnss to files package
Features related to standard formats (i.e., CCSDS, ILRS, SINEX, and SP3) are in files package. However, RINEX format is in gnss. It shall be moved to files in order to improve consistency.
See forum discussion: https://forum.orekit.org/t/moving-rinex-parser-to-files-package/2765