Only apply range part of PC matern prior once if range is shared

[seananderson]

See this issue for more details: https://github.com/pbs-assess/sdmTMB/issues/95

The TMB code is there, it's just a matter of only applying the range part once if needed.

[seananderson]

This is done. Thanks @ericward-noaa. I'm not 100% sure if the Jacobian adjustment parts also need to be conditionally applied. If so, it isn't obvious to me how given they are split up as P(sigma) and P(sigma | range). e.g. https://github.com/pbs-assess/sdmTMB/issues/95#issuecomment-1138597510