[MLIR][Linalg] Make detensoring cost-model more flexible.

So far, the CF cost-model for detensoring was limited to discovering
pure CF structures. This means, if while discovering the CF component,
the cost-model found any op that is not detensorable, it gives up on
detensoring altogether. This patch makes it a bit more flexible by
cleaning-up the detensorable component from non-detensorable ops without
giving up entirely.

Reviewed By: silvas

Differential Revision: https://reviews.llvm.org/D109965