JAZZ Dewey Redman Quartet. ''The Struggle Continues.'' Redman, tenor sax; Charles Eubanks, piano; Mark Helias, bass; Ed Blackwell, drums. (ECM 1-1225.) This is a Dewey Redman sampler. It's his first group album in five years and a lot more mainstream than what he has done, say, with Old and New Dreams band. The tunes run the gamut from the boppish ''Thren'' through the pretty ballad ''Love Is'' to the avant-gardeness of ''Combinations'' - something for everyone. Through it all, Dewey plays strongly, with a certain eccentric charm. There's lots of upper-register trilling, and a rather harsh, nasal, though not unpleasing sound in the higher regions. Unfortunately, one has the feeling that the sidemen felt a bit uncomfortable in this session, which mars somewhat an otherwise interesting set. All of the tunes, except Charlie Parker's ''Dewey Square,'' are by Redman.