[aot] Fixed C-API behavior tests (taichi-dev#6939)

Fixed allocation leakage, unchecked values, camel cases and
uninitialized structs in behavior tests. Reflected in codes, this PR has
done the following:

1. Use lifetime guarded C++ wrapper for usage that are *not* the tested
interface.
2. Removed several *success* tests that might overlap with those in
other tests. (This is not done completely, will make another PR to
refactorize that.)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

c_api/include/taichi/cpp/taichi.hpp

@@ -153,6 +153,21 @@ class Memory {
     unmap();
   }
 
+  TiMemorySlice slice(size_t offset, size_t size) const {
+    if (offset + size > size_) {
+      ti_set_last_error(TI_ERROR_ARGUMENT_OUT_OF_RANGE, "size");
+      return {};
+    }
+    TiMemorySlice slice{};
+    slice.memory = memory_;
+    slice.offset = offset;
+    slice.size = size;
+    return slice;
+  }
+  TiMemorySlice slice() const {
+    return slice(0, size_);
+  }
+
   constexpr size_t size() const {
     return size_;
   }
@@ -271,6 +286,13 @@ class NdArray {
     write((const T *)src.data(), src.size() * (sizeof(U) / sizeof(T)));
   }
 
+  TiMemorySlice slice(size_t offset, size_t size) const {
+    return memory_.slice(offset, size);
+  }
+  TiMemorySlice slice() const {
+    return memory_.slice();
+  }
+
   constexpr TiDataType elem_type() const {
     return ndarray_.elem_type;
   }