thermal: Update virtualtemp_estimator_test default thermal config.

Instead of directly relying on thermal_info_config check if property
vendor.thermal.config is set.
Update model_path and config_path to std::string from char*

Bug: 298225131
Test: Flash and run binary
Change-Id: Iab56b7894353927a583e7fd13f702241745390e9
1 file changed