[mlir][gpu] Allow distributing to different level of IDs without failing

[mlir][gpu] Allow distributing to different level of IDs without failing

Change map_nested_foreach_to_threads to ignore foreach_thread not
mapping to threads, this will allow us to call
mapNestedForeachToThreadsImpl with different set of ids to lower
multiple levels. Also adds warpIds attributes.

Differential Revision: https://reviews.llvm.org/D143298