Prepend kiss_icp_ for env variable usage

Before this didn't work
```
export DATA=carlos
kiss_icp_pipeline ...
```

After, you need to be more explicit to break it:
```
export KISS_ICP_DATA=carlos
kiss_icp_pipeline ...
```

This allow us to mantain the API as well

python/kiss_icp/config/parser.py

@@ -28,12 +28,13 @@
 from pathlib import Path
 from typing import Any, Dict, Optional
 
-from pydantic_settings import BaseSettings
+from pydantic_settings import BaseSettings, SettingsConfigDict
 
 from kiss_icp.config.config import AdaptiveThresholdConfig, DataConfig, MappingConfig
 
 
 class KISSConfig(BaseSettings):
+    model_config = SettingsConfigDict(env_prefix="kiss_icp_")
     out_dir: str = "results"
     data: DataConfig = DataConfig()
     mapping: MappingConfig = MappingConfig()