[mlir][sparse] use "current" and "curr" consistently (llvm#74656)

Removes at in favor of curr; also makes method delegates consistent

Author: aartbik

mlir/lib/Dialect/SparseTensor/Transforms/CodegenEnv.h

@@ -108,7 +108,7 @@ class CodegenEnv {
     return loopEmitter.unpackTensorLevelRange(std::forward<ContainerTy>(c));
   }
 
-  unsigned getLoopDepth() const { return loopEmitter.getCurrentDepth(); }
+  unsigned getCurrentDepth() const { return loopEmitter.getCurrentDepth(); }
 
   //
   // Code generation environment verify functions.