[mlir][tensor] Fix one-shot bufferization of tensor.reshape.

I believe that the previous implementation did not work on any input. It
called getMemRefType with `layout = {}`, presumably with the intention
to create a MemrefType with identity layout. However, the implementation
of that function returns a MemrefType with *unknown* layout if it is
provided with a default-constructed layout attribute. This patch uses
getMemRefTypeWithStaticIdentityLayout instead, with has identical
behavior except for the case of a default-constructed layout, which it
passes on as-is to the MemrefType.

This problem did not surface in the test because tensor.reshape was not
tested with -one-shot-bufferize. This patch introduces a test copied
from the tests for -tesnor-bufferize adapted in as follows: since the
test is run with "bufferize-function-boundaries", a tensor that is
passed into the function is bufferized into a memref with unknown
layout, which wouldn't be a valid intput for memref.reshape, so the
tests now uses a tensor constructed with arith.constant inside of the
function.

Reviewed By: springerm

Differential Revision: https://reviews.llvm.org/D151544