Use TeamVectorRange in tridiag solver.

[ambrad]

See #2070 for background on TeamVR.

Once TeamVR is used in the Hommexx and EKAT tridiag files, the arch-specific code in those files can be removed.

[ambrad]

I'm going to do the modifications as part of the mimc-GPU work so that I can do one overall performance check for both sets of changes.