[mlir][linalg][transform] Rename ApplyPatternsOp.{region => patterns}.

[ingomueller-net]

Summary

This gives the region a more meaningful name. The topic came up in a
discussion on https://reviews.llvm.org/D155435, where the name region
would have led to a situation where a convenience accessor called
region (after the ODS name) would have returned a Block.

mlir/include/mlir/Dialect/Transform/IR/TransformOps.td

let description = [{
     This transform also fails silently if the pattern application did not
     converge within the default number of iterations/rewrites of the greedy
     pattern rewrite driver.
   }];
 
   let arguments = (ins
     TransformHandleTypeInterface:$target);
   let results = (outs);
-  let regions = (region MaxSizedRegion<1>:$region);
+  let regions = (region MaxSizedRegion<1>:$patterns);
 
-  let assemblyFormat = "`to` $target $region attr-dict `:` type($target)";
+  let assemblyFormat = "`to` $target $patterns attr-dict `:` type($target)";
   let hasVerifier = 1;
 
   let skipDefaultBuilders = 1;
   let builders = [
     OpBuilder<(ins
         "Value":$target,
         CArg<"function_ref<void(OpBuilder &, Location)>", "nullptr">:
             $bodyBuilder)>,