Correct usage of ov::Tensor::data for 26.0 release (#2934)

## Description
- Update usage of ov::Tensor::data() member for OV 26.0 to fix build
issues.
- No test update, functionality not changed.
- No docs update required.

Blocked PR:
- openvinotoolkit/openvino#32569

<!--- Jira ticket number (e.g., 123). Delete if there's no ticket. Don't
include full link or project name. -->
Ticket: 
CVS-174872

## Checklist:
- [x] Tests have been updated or added to cover the new code <!--- If
the change isn't maintenance related, update the tests at
https://github.com/openvinotoolkit/openvino.genai/tree/master/tests or
explain in the description why the tests don't need an update. -->
- [x] This patch fully addresses the ticket. <!--- If follow-up pull
requests are needed, specify in description. -->
- [x] I have made corresponding changes to the documentation

Signed-off-by: Raasz, Pawel <pawel.raasz@intel.com>

Author: praasz

src/cpp/src/lora/adapter.cpp

@@ -100,9 +100,10 @@ struct AutoSafetensor: public safetensors_File {
 ConstantMap safetensor_to_constant_map(const ov::Tensor& safetensor) {
     AutoSafetensor safe_tensors_file{};
 
-    OPENVINO_ASSERT(safetensors_file_init(safetensor.data<char>(), safetensor.get_byte_size(), &safe_tensors_file) == nullptr,
-        "Cannot parse safetensor as a Safetensors file format. Safetensors file format is supported only"
-    );
+    // Intentionally discard constness as safetensors_file_init requires a non-const pointer (used as read-only)
+    auto data_ptr = const_cast<char*>(safetensor.data<char>());
+    OPENVINO_ASSERT(safetensors_file_init(data_ptr, safetensor.get_byte_size(), &safe_tensors_file) == nullptr,
+                    "Cannot parse safetensor as a Safetensors file format. Safetensors file format is supported only");
 
     ConstantMap tensors;
     for (int i = 0; i < safe_tensors_file.num_tensors; i++) {

src/cpp/src/speculative_decoding/speculative_decoding_stateful.cpp

@@ -338,7 +338,7 @@ std::variant<int64_t, std::vector<int64_t>>
 
     auto sample_token = [&](const ov::Tensor& logits, std::size_t idx) {
         size_t sequence_offset = idx * vocab_size;
-        float* logits_data = logits.data<float>() + sequence_offset;
+        const float* logits_data = logits.data<float>() + sequence_offset;
         return std::max_element(logits_data, logits_data + vocab_size) - logits_data;
     };