NVS: using esp_partition API

* partition api changed from spi_flash* API to
  esp_partition* API and is abstracted as a C++
  interface.
* The old nvs encryption is still possible
* changed default unit test app partition table
* Partitions coming from esp_partition API are
  checked for generic flash encryption. If yes,
  an error is returned since generic flash
  encryption isn't compatible with nvs
  encryption
* esp32, esp32s2 tests don't require nvs_flash
  but mbedtls now

Closes IDF-1340
Closes IDF-858

components/nvs_flash/src/nvs_partition_lookup.cpp

@@ -0,0 +1,65 @@
+#include "esp_partition.h"
+#include "nvs_partition_lookup.hpp"
+
+#ifdef CONFIG_NVS_ENCRYPTION
+#include "nvs_encrypted_partition.hpp"
+#endif // CONFIG_NVS_ENCRYPTION
+
+namespace nvs {
+
+esp_err_t lookup_nvs_partition(const char* label, NVSPartition **p)
+{
+    const esp_partition_t* esp_partition = esp_partition_find_first(
+            ESP_PARTITION_TYPE_DATA, ESP_PARTITION_SUBTYPE_DATA_NVS, label);
+
+    if (esp_partition == nullptr) {
+        return ESP_ERR_NOT_FOUND;
+    }
+
+    if (esp_partition->encrypted) {
+        return ESP_ERR_NVS_WRONG_ENCRYPTION;
+    }
+
+    NVSPartition *partition = new (std::nothrow) NVSPartition(esp_partition);
+    if (partition == nullptr) {
+        return ESP_ERR_NO_MEM;
+    }
+
+    *p = partition;
+
+    return ESP_OK;
+}
+
+#ifdef CONFIG_NVS_ENCRYPTION
+esp_err_t lookup_nvs_encrypted_partition(const char* label, nvs_sec_cfg_t* cfg, NVSPartition **p)
+{
+    const esp_partition_t* esp_partition = esp_partition_find_first(
+            ESP_PARTITION_TYPE_DATA, ESP_PARTITION_SUBTYPE_DATA_NVS, label);
+
+    if (esp_partition == nullptr) {
+        return ESP_ERR_NOT_FOUND;
+    }
+
+    if (esp_partition->encrypted) {
+        return ESP_ERR_NVS_WRONG_ENCRYPTION;
+    }
+
+    NVSEncryptedPartition *enc_p = new (std::nothrow) NVSEncryptedPartition(esp_partition);
+    if (enc_p == nullptr) {
+        return ESP_ERR_NO_MEM;
+    }
+
+    esp_err_t result = enc_p->init(cfg);
+    if (result != ESP_OK) {
+        delete enc_p;
+        return result;
+    }
+
+    *p = enc_p;
+
+    return ESP_OK;
+}
+
+#endif // CONFIG_NVS_ENCRYPTION
+
+} // nvs